hasdata
Determine whether data is available to read
Syntax
Description
Examples
Inspect and Analyze SimulationDatastore
Object Data
You can log big data from a simulation and inspect and analyze portions of that data by interacting with a matlab.io.datastore.SimulationDatastore
object.
Log Big Data from Model
Open the model sldemo_fuelsys
.
mdl = "sldemo_fuelsys";
open_system(mdl)
Select Configuration Parameters > Data Import/Export > Log Dataset data to file to log data to persistent storage. Alternatively, you can log data using Dataset
format to a MAT-file instead of the workspace programmatically.
set_param(mdl,"LoggingToFile","on")
Simulate the model.
sim(mdl);
The MAT-file out.mat
appears in your current folder. Logged signal data is stored in the MAT-file with the variable name sldemo_fuelsys_out
.
Create a DatasetRef
object that refers to the logged signal data.
DSRef = Simulink.SimulationData.DatasetRef("out.mat","sldemo_fuelsys_output");
Preview Big Data
Use curly braces to return a SimulationDatastore
representation of the fuel
signal, which is the tenth element in the DatasetRef
object DSRef
. The SimulationDatastore
object exists in the Values
property of the returned Signal
object.
SimDataSig = DSRef{10}; DStore = SimDataSig.Values;
Use the preview
function to inspect the first ten samples of logged data for the fuel
signal.
preview(DStore)
ans=10×1 timetable
Time Data
______________ ______
0 sec 1.2855
0.00056195 sec 1.2855
0.0033717 sec 1.2855
0.01 sec 1.2398
0.02 sec 1.199
0.03 sec 1.1628
0.04 sec 1.1309
0.043098 sec 1.1309
0.043098 sec 1.1309
0.043098 sec 1.1309
Inspect Specific Sample
Suppose you want to inspect the 603rd sample of logged fuel
data. Set the ReadSize
property of DStore
to a number that, considering memory resources, your computer can tolerate. For example, set ReadSize
to 200
.
DStore.ReadSize = 200;
Read from the datastore three times. Each read operation advances the reading position by 200 samples.
read(DStore); read(DStore); read(DStore);
Now that you are close to the 603rd sample, you can set ReadSize
to a smaller number to make the target sample easier to find. For example, set ReadSize
to 5
.
DStore.ReadSize = 5;
Read from the datastore again. The third sample of read data is the 603rd sample in the datastore.
read(DStore)
ans=5×1 timetable
Time Data
________ ______
5.83 sec 1.6609
5.84 sec 1.6733
5.85 sec 1.6831
5.86 sec 1.691
5.87 sec 1.6975
Inspect Earlier Sample
You can also inspect an earlier sample. For example, inspect the 403rd sample of logged fuel
data. Due to previous read operations, the datastore now reads starting from the 606th sample.
Use the reset
function to reset DStore
. Then, read from the first sample up to the 403rd sample.
reset(DStore);
Set ReadSize
to 200
.
DStore.ReadSize = 200;
Read from the datastore twice to advance the read position to the 401st sample.
read(DStore); read(DStore);
Set ReadSize
to 5
and read from the datastore. Now, the third sample of read data is the 403rd sample in the datastore.
DStore.ReadSize = 5; read(DStore)
ans=5×1 timetable
Time Data
________ _______
3.86 sec 0.9895
3.87 sec 0.98253
3.88 sec 0.97559
3.89 sec 0.96867
3.9 sec 0.96178
Extract Multiple Samples
You can also use the read
function to extract multiple samples. For example, extract samples 1001 through 1020.
Reset the datastore. Then, advance to sample 1001 by setting the ReadSize
property to 200
and reading the datastore five times.
reset(DStore) DStore.ReadSize = 200; for i = 1:5 read(DStore); end
Set the ReadSize
to 20
to extract 20 samples from the datastore.
DStore.ReadSize = 20;
Extract samples 1001 through 1020. Store the extracted data in a variable named targetSamples
.
targetSamples = read(DStore)
targetSamples=20×1 timetable
Time Data
________ ______
9.77 sec 1.68
9.78 sec 1.6856
9.79 sec 1.6905
9.8 sec 1.6948
9.81 sec 1.6812
9.82 sec 1.6714
9.83 sec 1.6642
9.84 sec 1.659
9.85 sec 1.6553
9.86 sec 1.6527
9.87 sec 1.6684
9.88 sec 1.6806
9.89 sec 1.6904
9.9 sec 1.6982
9.91 sec 1.7047
9.92 sec 1.7101
⋮
Find Maximum Value of Data in Datastore
Use the hasdata
function as the condition for a while
loop to incrementally analyze the data in chunks of 200 samples.
reset(DStore); DStore.ReadSize = 200; runningMax = []; while hasdata(DStore) tt = read(DStore); rawChunk = tt.Data; runningMax = max([rawChunk; runningMax]); end
The variable runningMax
stores the maximum value in the entire datastore.
runningMax
runningMax = 1.7291
Process Signal Data Using matlab.io.datastore.sdidatastore
Object
A matlab.io.datastore.sdidatastore
object references signal data in the Simulation Data Inspector repository. When the signal is too large to fit into memory, you can use the sdidatastore
object to incrementally process the data manually or to create a tall timetable for the signal that handles the incremental processing for you.
Create sdidatastore
for Signal
Simulate the sldemo_fuelsys
model, which is configured to log several signals, to create data in the Simulation Data Inspector repository.
mdl = "sldemo_fuelsys";
sim(mdl);
Logged signal data is returned in a Simulink.SimulationData.Dataset
object named sldemo_fuelsys_output
.
sldemo_fuelsys_output
sldemo_fuelsys_output = Simulink.SimulationData.Dataset 'sldemo_fuelsys_output' with 10 elements Name BlockPath ______________ ________________________________________ 1 [1x1 Signal] '' sldemo_fuelsys/EGO Fault Switch 2 [1x1 Signal] air_fuel_ratio sldemo_fuelsys/Engine Gas Dynamics 3 [1x1 Signal] '' sldemo_fuelsys/Engine Speed Fault Switch 4 [1x1 Signal] speed sldemo_fuelsys/Engine_Speed_Selector 5 [1x1 Signal] '' sldemo_fuelsys/MAP Fault Switch 6 [1x1 Signal] map sldemo_fuelsys/MAP_Selector 7 [1x1 Signal] ego sldemo_fuelsys/O2_Voltage_Selector 8 [1x1 Signal] '' ...o_fuelsys/Throttle Angle Fault Switch 9 [1x1 Signal] throttle sldemo_fuelsys/Throttle_Angle_Selector 10 [1x1 Signal] fuel sldemo_fuelsys/To Plant - Use braces { } to access, modify, or add elements using index.
Use the Simulation Data Inspector programmatic interface to get the signal ID for the signal named speed
.
runCount = Simulink.sdi.getRunCount;
latestRunID = Simulink.sdi.getRunIDByIndex(runCount);
latestRun = Simulink.sdi.getRun(latestRunID);
speedSigID = getSignalIDsByName(latestRun,"speed");
Use the signal ID to create an sdidatastore
object for the speed
signal.
speedSDIds = matlab.io.datastore.sdidatastore(speedSigID);
Verify Contents of Datastore
Check the Name
property of the sdidatastore
object to verify that it matches your expectations.
speedSDIds.Name
ans = 'speed'
You can also use the preview
function to verify the first ten samples in the signal.
preview(speedSDIds)
ans=10×1 timetable
Time Data
______________ ______
0 sec 314.16
0.00056195 sec 314.16
0.0033717 sec 314.16
0.01 sec 314.16
0.02 sec 314.16
0.03 sec 314.16
0.04 sec 314.16
0.043098 sec 314.16
0.043098 sec 314.16
0.043098 sec 314.16
Process Signal Data with sdidatastore
Object
When your signal is too large to fit into memory, you can use the read
function to read chunks of data from the Simulation Data Inspector repository to incrementally process your data. Use the hasdata
function as the condition for a while loop to incrementally process the whole signal. For example, find the maximum signal value.
latestMax = []; while hasdata(speedSDIds) speedChunk = read(speedSDIds); speedChunkData = speedChunk.Data; latestMax = max([speedChunkData; latestMax]); end latestMax
latestMax = 314.1593
On each read operation, the read
function updates the read position for the start of the next read operation. After reading some or all of the sdidatastore
object, you can reset the read position to start again from the beginning of the signal.
reset(speedSDIds)
Process Signal Data in Memory
When the signal referenced by your sdidatastore
object fits into memory, you can use the readall
function to read all the signal data into memory for processing rather than reading and processing the data incrementally with the read
function. The readall
function returns a timetable
with all the signal data.
speedTimetable = readall(speedSDIds); speedMax = max(speedTimetable.Data)
speedMax = 314.1593
Input Arguments
dst
— Datastore
matlab.io.datastore.sdidatastore
object | matlab.io.datastore.simulationdatastore
object
Datastore to check for available data to read, specified as a
matlab.io.datastore.sdidatastore
or
matlab.io.datastore.simulationdatastore
object.
Output Arguments
tf
— Data availability indication
1
| 0
Data availability indication, returned as a 1
or
0
of data type logical
. When the
sdidatastore
object has data available to read,
tf
is 1
. When data is not
available, tf
is 0
.
Version History
Introduced in R2017b
See Also
Objects
matlab.io.datastore.sdidatastore
|matlab.io.datastore.SimulationDatastore
|Simulink.sdi.DatasetRef
Functions
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