# estimate

Fit conditional variance model to data

## Syntax

## Description

returns the fully specified, estimated conditional variance model
`EstMdl`

= estimate(`Mdl`

,`y`

)`EstMdl`

. This model stores the estimated parameter values
resulting from fitting the partially specified conditional variance model
`Mdl`

to the observed univariate time series
`y`

by using maximum likelihood.
`EstMdl`

and `Mdl`

are the same model
type and have the same structure (see `garch`

, `egarch`

, and `gjr`

).

fits the partially specified conditional variance model `EstMdl`

= estimate(`Mdl`

,`Tbl1`

)`Mdl`

to response variable in the input table or timetable `Tbl1`

,
which contains time series data, and returns the fully specified, estimated
conditional variance model `EstMdl`

.
`estimate`

selects the response variable named in
`Mdl.SeriesName`

or the sole variable in
`Tbl1`

. To select a different response variable in
`Tbl1`

to fit the model to, use the
`ResponseVariable`

name-value argument.* (since R2023a)*

`[___] = estimate(___,`

specifies options using one or more name-value arguments in
addition to any of the input argument combinations in previous syntaxes.
`Name,Value`

)`estimate`

returns the output argument combination for the
corresponding input arguments. For example, `estimate(Mdl,y,Y0=y0)`

fits the
conditional variance model `Mdl`

to the vector of response data
`y`

, and specifies the vector of presample response data
`y0`

.

Supply all input data using the same data type. Specifically:

If you specify the numeric vector

`y`

, optional data sets must be numeric arrays and you must use the appropriate name-value argument. For example, to specify a presample, set the`Y0`

name-value argument to a numeric matrix of presample data.If you specify the table or timetable

`Tbl1`

, optional data sets must be tables or timetables, respectively, and you must use the appropriate name-value argument. For example, to specify a presample, set the`Presample`

name-value argument to a table or timetable of presample data.

## Examples

### Fit GARCH Model to Vector of Response Data

Fit a GARCH(1,1) model to a simulated vector of data.

Simulate 500 data points from the GARCH(1,1) model

$${y}_{t}={\epsilon}_{t},$$

where $${\epsilon}_{t}={\sigma}_{t}{z}_{t}$$ and

$${\sigma}_{t}^{2}=0.0001+0.5{\sigma}_{t-1}^{2}+0.2{\epsilon}_{t-1}^{2}.$$

Use the default Gaussian innovation distribution for $${z}_{t}$$.

Mdl0 = garch(Constant=0.0001,GARCH=0.5,ARCH=0.2); rng("default") % For reproducibility [v,y] = simulate(Mdl0,500);

The output `v`

contains simulated conditional variances. `y`

is a column vector of simulated responses (innovations).

Specify a GARCH(1,1) model with unknown coefficients, and fit it to the series `y`

.

Mdl = garch(1,1); EstMdl = estimate(Mdl,y)

GARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 9.8911e-05 3.0726e-05 3.2191 0.001286 GARCH{1} 0.45394 0.11193 4.0557 4.9987e-05 ARCH{1} 0.26374 0.056931 4.6326 3.6111e-06

EstMdl = garch with properties: Description: "GARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 9.89108e-05 GARCH: {0.453936} at lag [1] ARCH: {0.263739} at lag [1] Offset: 0

The result is a new `garch`

model called `EstMdl`

. The parameter estimates in `EstMdl`

resemble the parameter values that generated the simulated data.

### Estimate EGARCH Model Parameters Without Initial Values

Fit an EGARCH(1,1) model to simulated data.

Simulate 500 data points from an EGARCH(1,1) model

$${y}_{t}={\epsilon}_{t},$$

where $${\epsilon}_{t}={\sigma}_{t}{z}_{t},$$ and

$$\mathrm{log}{\sigma}_{t}^{2}=0.001+0.7\mathrm{log}{\sigma}_{t-1}^{2}+0.5\left[\frac{\left|{\epsilon}_{t-1}\right|}{{\sigma}_{t-1}}-\sqrt{\frac{2}{\pi}}\right]-0.3\left(\frac{{\epsilon}_{t-1}}{{\sigma}_{t-1}}\right)$$

(the distribution of $${z}_{t}$$ is Gaussian).

Mdl0 = egarch(Constant=0.001,GARCH=0.7, ... ARCH=0.5,Leverage=-0.3); rng("default") % For reproducibility [v,y] = simulate(Mdl0,500);

The output `v`

contains simulated conditional variances. `y`

is a column vector of simulated responses (innovations).

Specify an EGARCH(1,1) model with unknown coefficients, and fit it to the series `y`

.

Mdl = egarch(1,1); EstMdl = estimate(Mdl,y)

EGARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue ___________ _____________ __________ __________ Constant -0.00063867 0.031698 -0.020149 0.98392 GARCH{1} 0.70506 0.067359 10.467 1.2221e-25 ARCH{1} 0.56774 0.074746 7.5956 3.063e-14 Leverage{1} -0.32116 0.053345 -6.0204 1.7399e-09

EstMdl = egarch with properties: Description: "EGARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: -0.00063867 GARCH: {0.705065} at lag [1] ARCH: {0.567741} at lag [1] Leverage: {-0.321158} at lag [1] Offset: 0

The result is a new `egarch`

model called `EstMdl`

. The parameter estimates in `EstMdl`

resemble the parameter values that generated the simulated data.

### Estimate GJR Model Parameters Without Initial Values

Fit a GJR(1,1) model to simulated data.

Simulate 500 data points from a GJR(1,1) model.

$${y}_{t}={\epsilon}_{t},$$

where $${\epsilon}_{t}={\sigma}_{t}{z}_{t}$$ and

$${\sigma}_{t}^{2}=0.001+0.5{\sigma}_{t-1}^{2}+0.2{\epsilon}_{t-1}^{2}+0.2I\left[{\epsilon}_{t-1}<0\right]{\epsilon}_{t-1}^{2}.$$

Use the default Gaussian innovation distribution for $${z}_{t}$$.

Mdl0 = gjr(Constant=0.001,GARCH=0.5, ... ARCH=0.2,Leverage=0.2); rng("default") % For reproducibility [v,y] = simulate(Mdl0,500);

The output `v`

contains simulated conditional variances. `y`

is a column vector of simulated responses (innovations).

Specify a GJR(1,1) model with unknown coefficients, and fit it to the series `y`

.

Mdl = gjr(1,1); EstMdl = estimate(Mdl,y)

GJR(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 0.00097382 0.00025135 3.8743 0.00010694 GARCH{1} 0.46055 0.071793 6.4151 1.4077e-10 ARCH{1} 0.24126 0.063409 3.8047 0.00014196 Leverage{1} 0.25051 0.11265 2.2237 0.02617

EstMdl = gjr with properties: Description: "GJR(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 0.000973819 GARCH: {0.460555} at lag [1] ARCH: {0.241256} at lag [1] Leverage: {0.250507} at lag [1] Offset: 0

The result is a new `gjr`

model called `EstMdl`

. The parameter estimates in `EstMdl`

resemble the parameter values that generated the simulated data.

### Estimate GARCH Model Parameters Using Presample Data

Fit a GARCH(1,1) model to the daily close NASDAQ Composite Index returns.

Load the NASDAQ data included with the toolbox. Convert the index to returns.

load Data_EquityIdx nasdaq = DataTable.NASDAQ; y = price2ret(nasdaq); T = length(y); figure plot(y) xlim([0,T]) title("NASDAQ Returns")

The returns exhibit volatility clustering.

Specify a GARCH(1,1) model, and fit it to the series. One presample innovation is required to initialize this model. Use the first observation of `y`

as the necessary presample innovation.

Mdl = garch(1,1); [EstMdl,EstParamCov] = estimate(Mdl,y(2:end),E0=y(1))

GARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 1.9987e-06 5.4228e-07 3.6857 0.00022807 GARCH{1} 0.88356 0.0084341 104.76 0 ARCH{1} 0.10903 0.0076471 14.257 4.0407e-46

EstMdl = garch with properties: Description: "GARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 1.99867e-06 GARCH: {0.883563} at lag [1] ARCH: {0.109027} at lag [1] Offset: 0

EstParamCov =3×310^{-4}× 0.0000 -0.0000 0.0000 -0.0000 0.7113 -0.5343 0.0000 -0.5343 0.5848

The output `EstMdl`

is a new `garch`

model with estimated parameters.

Use the output variance-covariance matrix to calculate the estimate standard errors.

se = sqrt(diag(EstParamCov))

`se = `*3×1*
0.0000
0.0084
0.0076

These are the standard errors shown in the estimation output display. They correspond (in order) to the constant, GARCH coefficient, and ARCH coefficient.

### Estimate EGARCH Model Parameters Using Presample Data

Fit an EGARCH(1,1) model to the daily close NASDAQ Composite Index returns.

Load the NASDAQ data included with the toolbox. Convert the index to returns.

load Data_EquityIdx nasdaq = DataTable.NASDAQ; y = price2ret(nasdaq); T = length(y); figure plot(y) xlim([0,T]) title("NASDAQ Returns")

The returns exhibit volatility clustering.

Specify an EGARCH(1,1) model, and fit it to the series. One presample innovation is required to initialize this model. Use the first observation of `y`

as the necessary presample innovation.

Mdl = egarch(1,1); [EstMdl,EstParamCov] = estimate(Mdl,y(2:end),E0=y(1))

EGARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue _________ _____________ __________ __________ Constant -0.13478 0.022092 -6.101 1.0539e-09 GARCH{1} 0.98391 0.0024221 406.22 0 ARCH{1} 0.19964 0.013966 14.296 2.3323e-46 Leverage{1} -0.060243 0.005647 -10.668 1.4355e-26

EstMdl = egarch with properties: Description: "EGARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: -0.134784 GARCH: {0.983909} at lag [1] ARCH: {0.199645} at lag [1] Leverage: {-0.0602431} at lag [1] Offset: 0

EstParamCov =4×410^{-3}× 0.4881 0.0533 -0.1018 0.0106 0.0533 0.0059 -0.0118 0.0017 -0.1018 -0.0118 0.1950 0.0016 0.0106 0.0017 0.0016 0.0319

The output `EstMdl`

is a new `egarch`

model with estimated parameters.

Use the output variance-covariance matrix to calculate the estimate standard errors.

se = sqrt(diag(EstParamCov))

`se = `*4×1*
0.0221
0.0024
0.0140
0.0056

These are the standard errors shown in the estimation output display. They correspond (in order) to the constant, GARCH coefficient, ARCH coefficient, and leverage coefficient.

### Fit GARCH Model to Response Variable in Timetable

*Since R2023a*

Fit a GARCH(1,1) model to the average weekly closing NASDAQ returns. Supply a timetable of data and specify the series for the fit.

Load the U.S. equity indices data `Data_EquityIdx.mat`

.

`load Data_EquityIdx`

The timetable `DataTimeTable`

contains the daily NASDAQ closing prices, among other indices.

Compute the weekly average closing prices of all timetable variables.

`DTTW = convert2weekly(DataTimeTable,Aggregation="mean");`

Compute the weekly returns.

DTTRet = price2ret(DTTW); T = height(DTTRet)

T = 626

Plot the weekly NASDAQ returns.

```
figure
plot(DTTRet.Time,DTTRet.NASDAQ)
title("NASDAQ Weekly Returns")
```

The returns exhibit volatility clustering.

When you plan to supply a timetable, you must ensure it has all the following characteristics:

The selected response variable is numeric and does not contain any missing values.

The timestamps in the

`Time`

variable are regular, and they are ascending or descending.

Remove all missing values from the timetable, relative to the NASDAQ returns series.

```
DTTRet = rmmissing(DTTRet,DataVariables="NASDAQ");
numobs = height(DTTRet)
```

numobs = 626

Because all sample times have observed NASDAQ returns, `rmmissing`

does not remove any observations.

Determine whether the sampling timestamps have a regular frequency and are sorted.

`areTimestampsRegular = isregular(DTTRet,"weeks")`

`areTimestampsRegular = `*logical*
1

areTimestampsSorted = issorted(DTTRet.Time)

`areTimestampsSorted = `*logical*
1

`areTimestampsRegular = 1`

indicates that the timestamps of `DTTRet`

represent a regular weekly sample. `areTimestampsSorted = 1`

indicates that the timestamps are sorted.

Specify a GARCH(1,1) model, and fit it to the series. Specify the entire timetable of returns and select the variable containing the NASDAQ returns.

```
Mdl = garch(1,1);
[EstMdl,EstParamCov] = estimate(Mdl,DTTRet,ResponseVariable="NASDAQ")
```

GARCH(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ __________ Constant 1.7406e-06 8.9077e-07 1.9541 0.050694 GARCH{1} 0.65947 0.059314 11.118 1.0229e-28 ARCH{1} 0.33773 0.079595 4.2431 2.2044e-05

EstMdl = garch with properties: Description: "GARCH(1,1) Conditional Variance Model (Gaussian Distribution)" SeriesName: "Y" Distribution: Name = "Gaussian" P: 1 Q: 1 Constant: 1.74062e-06 GARCH: {0.659467} at lag [1] ARCH: {0.337731} at lag [1] Offset: 0

`EstParamCov = `*3×3*
0.0000 -0.0000 0.0000
-0.0000 0.0035 -0.0039
0.0000 -0.0039 0.0063

### Specify Presample Data In Timetable

*Since R2023a*

Fit a GJR(1,1) model to the average weekly closing NASDAQ returns. Specify in-sample and presample data in a timetable.

Load the U.S. equity indices data `Data_EquityIdx.mat`

.

`load Data_EquityIdx`

The timetable `DataTimeTable`

contains the daily NASDAQ closing prices, among other indices.

Compute the weekly average closing prices of all timetable variables.

`DTTW = convert2weekly(DataTimeTable,Aggregation="mean");`

Compute the weekly returns.

DTTRet = price2ret(DTTW); T = height(DTTRet)

T = 626

Plot the weekly NASDAQ returns.

```
figure
plot(DTTRet.Time,DTTRet.NASDAQ)
title("NASDAQ Weekly Returns")
```

The returns exhibit volatility clustering.

When you plan to supply a timetable, you must ensure it has all the following characteristics:

The selected response variable is numeric and does not contain any missing values.

The timestamps in the

`Time`

variable are regular, and they are ascending or descending.

Remove all missing values from the timetable, relative to the NASDAQ returns series.

```
DTTRet = rmmissing(DTTRet,DataVariables="NASDAQ");
numobs = height(DTTRet)
```

numobs = 626

Because all sample times have observed NASDAQ returns, `rmmissing`

does not remove any observations.

Determine whether the sampling timestamps have a regular frequency and are sorted.

`areTimestampsRegular = isregular(DTTRet,"weeks")`

`areTimestampsRegular = `*logical*
1

areTimestampsSorted = issorted(DTTRet.Time)

`areTimestampsSorted = `*logical*
1

`areTimestampsRegular = 1`

indicates that the timestamps of `DTTRet`

represent a regular weekly sample. `areTimestampsSorted = 1`

indicates that the timestamps are sorted.

Because $\mathrm{max}(p,q)=1$, one presample innovation is required to initialize this model. Partition the timetable of data into sets containing required presample and insample observations.

numpreobs = 1; DTTRetPresample = DTTRet(1:numpreobs,:); DTTRetInsample = DTTRet((numpreobs+1):end,:);

Specify a GJR(1,1) model, and fit it to the series. Specify the timetables of NASDAQ weekly returns for the required presample innovations and in-sample data.

Mdl = gjr(1,1); [EstMdl,EstParamCov] = estimate(Mdl,DTTRetInsample,Presample=DTTRetPresample, ... ResponseVariable="NASDAQ",PresampleInnovationVariable="NASDAQ");

GJR(1,1) Conditional Variance Model (Gaussian Distribution): Value StandardError TStatistic PValue __________ _____________ __________ ___________ Constant 6.5074e-07 5.1457e-07 1.2646 0.20601 GARCH{1} 0.79141 0.030886 25.623 8.3928e-145 ARCH{1} 0.090048 0.032478 2.7725 0.0055619 Leverage{1} 0.1808 0.048516 3.7266 0.0001941

The output `EstMdl`

is a new `gjr`

model with estimated parameters.

Use the output variance-covariance matrix to calculate the estimate standard errors.

se = sqrt(diag(EstParamCov))

`se = `*4×1*
0.0000
0.0309
0.0325
0.0485

These are the standard errors shown in the estimation output display. They correspond (in order) to the constant, GARCH coefficient, ARCH coefficient, and leverage coefficient.

## Input Arguments

`Mdl`

— Partially specified conditional variance model

`garch`

model object | `egarch`

model object | `gjr`

model object

Partially specified conditional variance model containing unknown
parameters, specified as a `garch`

, `egarch`

, or `gjr`

model object. Properties of
`Mdl`

describe the model structure and can specify
parameter values.

`estimate`

fits unspecified
(`NaN`

-valued) parameters to the data
`y`

.

`estimate`

treats specified parameters as equality
constraints during estimation.

`y`

— Single path of observed response data *y*_{t}

numeric column vector

_{t}

Single path of observed response data
*y _{t}*, to which the conditional
variance model

`Mdl`

is fit, specified as a
`numobs`

-by-1 numeric column vector.
`y`

represents `numobs`

observations
of a univariate time series.`y`

is usually a mean 0 series of innovations or
residuals and conditional variance characterized by the conditional variance
model `Mdl`

. In this case, `y`

is a
continuation of the innovation series `E0`

.

`y`

can also represent an innovation series with mean 0
plus an offset. A nonzero value of `Mdl.Offset`

signals the
inclusion of an offset in `Mdl`

.

The last observation of `y`

is the latest
observation.

**Data Types: **`double`

`Tbl1`

— Time series data

table | timetable

*Since R2023a*

Time series data containing response variable
*y _{t}*, to which

`estimate`

fits the conditional variance model
`Mdl`

, specified as a table or timetable with
`numvars`

variables and `numobs`

rows.
You can optionally select a response variable by using the
`ResponseVariable`

name-value argument.The selected response variable in `Tbl1`

is a numeric
vector representing a single path of `numobs`

observations.

Each row is an observation, and measurements in each row occur simultaneously.

If `Tbl1`

is a timetable, it must represent a sample
with a regular datetime time step (see `isregular`

), and the datetime
vector `Tbl1.Time`

must be strictly ascending or
descending.

If `Tbl1`

is a table, the last row contains the latest
observation.

### Name-Value Arguments

Specify optional pairs of arguments as
`Name1=Value1,...,NameN=ValueN`

, where `Name`

is
the argument name and `Value`

is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.

*
Before R2021a, use commas to separate each name and value, and enclose*
`Name`

*in quotes.*

**Example: **`Display="iter",E0=[0.1; 0.05]`

specifies to display
iterative optimization information, and `[0.05; 0.1]`

as presample
innovations.

**For GARCH, EGARCH, and GJR Models**

`ResponseVariable`

— Variable to select from `Tbl1`

to treat as response variable *y*_{t}

string scalar | character vector | integer | logical vector

_{t}

*Since R2023a*

Variable to select from `Tbl1`

to treat as the response variable
*y _{t}*, specified as one of the following
data types:

String scalar or character vector containing a variable name in

`Tbl1.Properties.VariableNames`

Variable index (integer) to select from

`Tbl1.Properties.VariableNames`

A length

`numvars`

logical vector, where`ResponseVariable(`

selects variable) = true`j`

from`j`

`Tbl1.Properties.VariableNames`

, and`sum(ResponseVariable)`

is`1`

The selected variable must be a numeric vector and cannot contain missing values (`NaN`

).

If `Tbl1`

has one variable, the default specifies that variable. Otherwise, the default matches the variable to name in `Mdl.SeriesName`

.

**Example: **`ResponseVariable="StockRate2"`

**Example: **`ResponseVariable=[false false true false]`

or `ResponseVariable=3`

selects the third table variable as the response variable.

**Data Types: **`double`

| `logical`

| `char`

| `cell`

| `string`

`E0`

— Presample innovations

numeric column vector

Presample innovations *ε _{t}*,
specified as a

`numpreobs`

-by-1 numeric column vector.
The presample innovations provide initial values for the innovations
process of the conditional variance model `Mdl`

. The
presample innovations derive from a distribution with mean 0. Use
`E0`

only when you supply the vector of response
data `y`

.`numpreobs`

is the number of presample observations.
Each row is a presample observation. The last row contains the latest
presample observation. `numpreobs`

must be at least
`Mdl.Q`

. If `numpreobs`

>
`Mdl.Q`

, `estimate`

uses the
latest required number of observations only. The last element or row
contains the latest observation.

The defaults are:

For GARCH(

*P*,*Q*) and GJR(*P*,*Q*) models,`estimate`

sets any necessary presample innovations to the square root of the average squared value of the offset-adjusted response series`y`

.For EGARCH(

*P*,*Q*) models,`estimate`

sets any necessary presample innovations to zero.

**Data Types: **`double`

`V0`

— Presample conditional variances

positive numeric column vector

Presample conditional variances
*σ _{t}*

^{2}, specified as a

`numpreobs`

-by-1 positive column vector.
`V0`

provides initial values for conditional
variance process of the conditional variance model
`Mdl`

. Use `V0`

only when you
supply the vector of response data `y`

.Each row is a presample observation. The last row contains the latest presample observation.

For GARCH(

*P*,*Q*) and GJR(*P*,*Q*) models,`numpreobs`

must be at least`Mdl.P`

.For EGARCH(

*P*,*Q*) models,`numpreobs`

must be at least`max([Mdl.P Mdl.Q])`

.

If `numpreobs`

exceeds the minimum
number, `estimate`

uses only the latest
observations. The last element or row contains the latest
observation.

By default, `estimate`

sets the necessary
presample conditional variances to the average squared value of the
offset-adjusted response series `y`

.

**Data Types: **`double`

`Presample`

— Presample data

table | timetable

*Since R2023a*

Presample data for innovations
*ε _{t}* or conditional
variances

*σ*

_{t}^{2}to initialize the model for estimation, specified as a table or timetable, the same type as

`Tbl1`

, with
`numprevars`

variables and
`numpreobs`

rows. Use
`Presample`

only when you supply a table or
timetable of data `Tbl1`

.Each selected variable is a single path of
`numpreobs`

observations representing the presample
of innovations or conditional variances for the selected response
variable in `Tbl1`

.

Each row is a presample observation, and measurements in each row
occur simultaneously. `numpreobs`

must be one of the
following values:

`Mdl.P`

when`Presample`

provides only presample conditional variances`Mdl.Q`

when`Presample`

provides only presample innovations`max([Mdl.P Mdl.Q])`

when`Presample`

provides presample innovations and conditional variances

If you supply more rows than necessary,
`estimate`

uses the latest required number of
observations only.

If `Presample`

is a timetable, all the following
conditions must be true:

`Presample`

must represent a sample with a regular datetime time step (see`isregular`

).The inputs

`Tbl1`

and`Presample`

must be consistent in time such that`Presample`

immediately precedes`Tbl1`

with respect to the sampling frequency and order.The datetime vector of sample timestamps

`Presample.Time`

must be ascending or descending.

If `Presample`

is a table, the last row contains
the latest presample observation.

By default:

For GARCH(

*P*,*Q*) and GJR(*P*,*Q*) models,`estimate`

sets any necessary presample innovations to the square root of the average squared value of the offset-adjusted response series`y`

.For EGARCH(

*P*,*Q*) models,`estimate`

sets any necessary presample innovations to zero.`estimate`

sets the necessary presample conditional variances to the average squared value of the offset-adjusted response series.

If you specify the `Presample`

, you must specify
the presample innovations or conditional variance variable names by
using the `PresampleInnovationVariable`

or
`PresampleVarianceVariable`

name-value
argument.

`PresampleInnovationVariable`

— Variable of `Presample`

containing data for the presample innovations *ε*_{t}

string scalar | character vector | integer | logical vector

_{t}

*Since R2023a*

Variable of `Presample`

containing data for the
presample innovations *ε _{t}*,
specified as one of the following data types:

String scalar or character vector containing the variable name to select from

`Presample.Properties.VariableNames`

Variable index (positive integer) to select from

`Presample.Properties.VariableNames`

A logical vector, where

`PresampleInnovationVariable(`

selects variable) = true`j`

from`j`

`Presample.Properties.VariableNames`

The selected variable must be a numeric vector and cannot contain
missing values (`NaN`

s).

If you specify presample innovations data by using the
`Presample`

name-value argument, you must specify
`PresampleInnovationVariable`

.

**Example: **`PresampleInnovationVariable="StockRateInnov0"`

**Example: **```
PresampleInnovationVariable=[false false true
false]
```

or `PresampleInnovationVariable=3`

selects the third table variable as the presample innovations
variable.

**Data Types: **`double`

| `logical`

| `char`

| `cell`

| `string`

`PresampleVarianceVariable`

— Variable of `Presample`

containing data for the presample conditional variances *σ*_{t}^{2}

string scalar | character vector | integer | logical vector

_{t}

*Since R2023a*

Variable of `Presample`

containing data for the presample conditional
variances
*σ _{t}*

^{2}, specified as one of the following data types:

String scalar or character vector containing a variable name in

`Presample.Properties.VariableNames`

Variable index (positive integer) to select from

`Presample.Properties.VariableNames`

A logical vector, where

`PresampleVarianceVariable(`

selects variable) = true`j`

from`j`

`Presample.Properties.VariableNames`

The selected variable must be a numeric vector and cannot contain missing values
(`NaN`

s).

If you specify presample conditional variance data by using the `Presample`

name-value argument, you must specify `PresampleVarianceVariable`

.

**Example: **`PresampleVarianceVariable="StockRateVar0"`

**Example: **`PresampleVarianceVariable=[false false true false]`

or `PresampleVarianceVariable=3`

selects the third table variable as the presample conditional variance variable.

**Data Types: **`double`

| `logical`

| `char`

| `cell`

| `string`

`Options`

— Optimization options

`optimoptions`

optimization controller

Optimization options, specified as an `optimoptions`

optimization
controller. For details on modifying the default values of the optimizer, see `optimoptions`

or `fmincon`

in Optimization Toolbox™.

For example, to change the constraint tolerance to `1e-6`

, set
```
options =
optimoptions(@fmincon,ConstraintTolerance=1e-6,Algorithm="sqp")
```

. Then,
pass `Options`

into `estimate`

using
`Options=options`

.

By default, `estimate`

uses the same default options as
`fmincon`

, except `Algorithm`

is
`"sqp"`

and `ConstraintTolerance`

is
`1e-7`

.

`Constant0`

— Initial conditional variance model constant estimate

numeric scalar

Initial conditional variance model constant estimate, specified as a numeric scalar.

For GARCH(*P*,*Q*) and
GJR(*P*,*Q*) models,
`Constant0`

must be a positive scalar.

By default, `estimate`

derives initial estimates
using standard time series techniques.

**Data Types: **`double`

`GARCH0`

— Initial coefficient estimates for past conditional variance terms

numeric vector

Initial coefficient estimates for past conditional variance terms, specified as a numeric vector.

For GARCH(

*P*,*Q*) and GJR(*P*,*Q*) models:`GARCH0`

must be a numeric vector containing nonnegative elements.`GARCH0`

contains the initial coefficient estimates associated with the past conditional variance terms that compose the GARCH polynomial.

For EGARCH(

*P*,*Q*) models,`GARCH0`

contains the initial coefficient estimates associated with past log conditional variance terms that compose the GARCH polynomial.

The number of coefficients in `GARCH0`

must equal the
number of lags associated with nonzero coefficients in the GARCH
polynomial, as specified in the `GARCHLags`

property of
`Mdl`

.

By default, `estimate`

derives initial estimates
using standard time series techniques.

**Data Types: **`double`

`ARCH0`

— Initial coefficient estimates corresponding to past innovation terms

numeric vector

Initial coefficient estimates corresponding to past innovation terms, specified as a numeric vector.

For GARCH(

*P*,*Q*) and GJR(*P*,*Q*) models:`ARCH0`

must be a numeric vector containing nonnegative elements.`ARCH0`

contains the initial coefficient estimates associated with the past squared innovation terms that compose the ARCH polynomial.By default,

`estimate`

derives initial estimates using standard time series techniques.

For EGARCH(

*P*,*Q*) models:`ARCH0`

contains the initial coefficient estimates associated with the magnitude of the past standardized innovations that compose the ARCH polynomial.By default,

`estimate`

sets the initial coefficient estimate associated with the first nonzero lag in the model to a small positive value. All other values are zero.

The number of coefficients in `ARCH0`

must equal the
number of lags associated with nonzero coefficients in the ARCH
polynomial, as specified in the `ARCHLags`

property of
`Mdl`

.

**Data Types: **`double`

`Offset0`

— Initial innovation mean model offset estimate

scalar

Initial innovation mean model offset estimate, specified as a scalar.

By default, `estimate`

sets the initial estimate
to the sample mean of `y`

.

**Data Types: **`double`

`DoF0`

— Initial estimate of *t*-distribution degrees-of-freedom parameter

`10`

(default) | positive scalar

Initial estimate of the *t*-distribution degrees-of-freedom parameter
*ν*, specified as a positive scalar. `DoF0`

must
exceed 2.

**Data Types: **`double`

`Display`

— Command Window display option

`"params"`

(default) | `"diagnostics"`

| `"full'"`

| `"iter"`

| `"off"`

| string vector | cell vector of character vectors

Command Window display option, specified as one or more of the values in this table.

Value | Information Displayed |
---|---|

`"diagnostics"` | Optimization diagnostics |

`"full"` | Maximum likelihood parameter estimates, standard errors, t statistics, iterative optimization information, and optimization diagnostics |

`"iter"` | Iterative optimization information |

`"off"` | None |

`"params"` | Maximum likelihood parameter estimates, standard errors, and
t statistics and p-values
of coefficient significance tests |

**Example: **`Display="off"`

is well suited for running a simulation that
estimates many models.

**Example: **`Display=["params" "diagnostics"]`

displays all estimation
results and the optimization diagnostics.

**Data Types: **`char`

| `cell`

| `string`

**For EGARCH and GJR Models**

`Leverage0`

— Initial coefficient estimates past leverage terms *ξ*

numeric vector

Initial coefficient estimates past leverage terms, specified as a numeric vector.

For EGARCH(*P*,*Q*) models,
`Leverage0`

contains the initial coefficient
estimates associated with past standardized innovation terms that
compose the leverage polynomial.

For GJR(*P*,*Q*) models,
`Leverage0`

contains the initial coefficient
estimates associated with past, squared, negative innovations that
compose the leverage polynomial.

The number of coefficients in `Leverage0`

must equal
the number of lags associated with nonzero coefficients in the leverage
polynomial (`Leverage`

), as specified in
`LeverageLags`

.

By default, `estimate`

sets the initial estimate
of the coefficient associated with the first non-zero lag in the model
to a small negative value, and it sets all others initial coefficients
to zero.

**Data Types: **`double`

**Note**

`NaN`

values in`Y`

,`E0`

, and`V0`

indicate missing values.`estimate`

removes missing values from specified data by list-wise deletion.For the presample,

`estimate`

horizontally concatenates`E0`

and`V0`

, and then it removes any row of the concatenated matrix containing at least one`NaN`

.For the estimation sample,

`estimate`

removes any row of`Y`

containing at least one`NaN`

.

This type of data reduction reduces the effective sample size and can create an irregular time series.

For numeric data inputs,

`estimate`

assumes that you synchronize the presample data such that the latest observations occur simultaneously.`estimate`

issues an error when any table or timetable input contains missing values.

## Output Arguments

`EstMdl`

— Conditional variance model containing parameter estimates

`garch`

model object | `egarch`

model object | `gjr`

model object

Conditional variance model containing parameter estimates, returned as a
`garch`

, `egarch`

, or `gjr`

model object.
`estimate`

uses maximum likelihood to calculate all
parameter estimates not constrained by `Mdl`

(i.e.,
constrained parameters have known values).

`EstMdl`

is a fully specified conditional variance model.
To infer conditional variances for diagnostic checking, pass
`EstMdl`

to `infer`

. To simulate or forecast
conditional variances, pass `EstMdl`

to `simulate`

or `forecast`

, respectively.

`EstParamCov`

— Variance-covariance matrix of maximum likelihood estimates

numeric matrix

Variance-covariance matrix of maximum likelihood estimates of model parameters known to the optimizer, returned as a numeric matrix.

The rows and columns associated with any parameters estimated by maximum likelihood contain the covariances of estimation error. The standard errors of the parameter estimates are the square root of the entries along the main diagonal.

The rows and columns associated with any parameters that are held fixed as
equality constraints contain `0`

s.

`estimate`

uses the outer product of
gradients (OPG) method to perform covariance matrix
estimation.

`estimate`

orders the parameters in
`EstParamCov`

as follows:

Constant

Nonzero GARCH coefficients at positive lags

Nonzero ARCH coefficients at positive lags

For EGARCH and GJR models, nonzero leverage coefficients at positive lags

Degrees of freedom (

*t*innovation distribution only)Offset (models with nonzero offset only)

**Data Types: **`double`

`logL`

— Optimized loglikelihood objective function value

scalar

Optimized loglikelihood objective function value, returned as a scalar.

**Data Types: **`double`

`info`

— Optimization summary

structure array

Optimization summary, returned as a structure array with the fields described in this table.

Field | Description |
---|---|

`exitflag` | Optimization exit flag (see `fmincon` in Optimization Toolbox) |

`options` | Optimization options controller (see `optimoptions` and `fmincon` in Optimization Toolbox) |

`X` | Vector of final parameter estimates |

`X0` | Vector of initial parameter estimates |

For example, you can display the vector of final estimates by entering `info.X`

in the Command Window.

**Data Types: **`struct`

## Tips

## Algorithms

If you do not specify the presample data (

`E0`

and`V0`

, or`Presample`

),`estimate`

derives the necessary presample observations from the unconditional, or long-run, variance of the offset-adjusted response process.For all conditional variance models, presample conditional variances are the sample average of the squared disturbances of the offset-adjusted response data.

For GARCH(

*P*,*Q*) and GJR(*P*,*Q*) models, presample innovations are the square root of the average squared value of the offset-adjusted response data.For EGARCH(

*P*,*Q*) models, presample innovations are`0`

.

These specifications minimize initial transient effects.

If you specify a value for the

`Display`

name-value argument, it takes precedence over the specifications of the optimization options`Diagnostics`

and`Display`

. Otherwise,`estimate`

honors all selections related to the display of optimization information in the optimization options.

## References

[1]
Bollerslev, Tim. “Generalized Autoregressive Conditional Heteroskedasticity.” *Journal of Econometrics* 31 (April 1986): 307–27. https://doi.org/10.1016/0304-4076(86)90063-1.

[2]
Bollerslev, Tim. “A Conditionally Heteroskedastic Time Series Model for Speculative Prices and Rates of Return.” *The Review of Economics and Statistics* 69 (August 1987): 542–47. https://doi.org/10.2307/1925546.

[3] Box, G. E. P., G. M. Jenkins, and G. C. Reinsel. *Time Series
Analysis: Forecasting and Control*. 3rd ed. Englewood Cliffs, NJ:
Prentice Hall, 1994.

[4] Enders, W. *Applied Econometric Time Series*. Hoboken, NJ:
John Wiley & Sons, 1995.

[5]
Engle, Robert. F. “Autoregressive Conditional Heteroscedasticity with Estimates of the Variance of United Kingdom Inflation.” *Econometrica* 50 (July 1982): 987–1007. https://doi.org/10.2307/1912773.

[6]
Glosten, L. R., R. Jagannathan, and D. E. Runkle. “On the Relation between the Expected Value and the Volatility of the Nominal Excess Return on Stocks.” *The Journal of Finance*. Vol. 48, No. 5, 1993, pp. 1779–1801.

[7] Greene, W. H. *Econometric Analysis*. 3rd ed. Upper Saddle
River, NJ: Prentice Hall, 1997.

[8]
Hamilton, James D. *Time Series Analysis*. Princeton, NJ: Princeton University Press, 1994.

## Version History

**Introduced in R2012a**

### R2023a: `estimate`

accepts input data in tables and timetables

In addition to accepting input data (in-sample and presample data) in numeric
arrays, `estimate`

accepts input data in tables or regular
timetables. When you supply data in a table or timetable,
`estimate`

chooses the default series on which to operate,
but you can use the specified optional name-value argument to select a different
series.

Name-value arguments to support tabular workflows include:

`ResponseVariable`

specifies the variable name of the response series in the input data`Tbl1`

, to which the model is fit.`Presample`

specifies the input table or timetable of presample innovations and conditional variance data.`PresampleInnovationVariable`

specifies the variable name of the innovations series to select from`Presample`

.`PresampleVarianceVariable`

specifies the variable name of the conditional variance series to select from`Presample`

.

### R2019b: `estimate`

includes the final lag in all estimated univariate time series model polynomials

`estimate`

includes the final polynomial lag as specified in the input model template for estimation. In other words, the specified polynomial degrees of an input model template returned by an object creation function and the corresponding polynomial degrees of the estimated model returned by estimate are equal.

Before R2019b, `estimate`

removed trailing lags estimated below the tolerance of `1e-12`

.

**Update Code**

Polynomial degrees require minimum presample observations for operations downstream of estimation, such as model forecasting and simulation. If a model template in your code does not describe the data generating process well, then the polynomials in the estimated model can have higher degrees than in previous releases. Consequently, you must supply additional presample responses for operations on the estimated model; otherwise, the function issues an error. For more details, see the `Y0`

name-value argument.

## See Also

### Objects

### Functions

### Topics

- Compare Conditional Variance Models Using Information Criteria
- Likelihood Ratio Test for Conditional Variance Models
- Estimate Conditional Mean and Variance Model
- Maximum Likelihood Estimation for Conditional Variance Models
- Conditional Variance Model Estimation with Equality Constraints
- Presample Data for Conditional Variance Model Estimation
- Initial Values for Conditional Variance Model Estimation
- Optimization Settings for Conditional Variance Model Estimation

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