Documentation

# andrewsplot

## Syntax

andrewsplot(X)
andrewsplot(X,...,'Standardize',standopt)
andrewsplot(X,...,'Quantile',alpha)
andrewsplot(X,...,'Group',group)
andrewsplot(X,...,'PropName',PropVal,...)
h = andrewsplot(X,...)

## Description

andrewsplot(X) creates an Andrews plot of the multivariate data in the matrix X. The rows of X correspond to observations, the columns to variables. Andrews plots represent each observation by a function f(t) of a continuous dummy variable t over the interval [0,1]. f(t) is defined for the ith observation in X as

$f\left(t\right)=X\left(i,1\right)/\sqrt{2}+X\left(i,2\right)\mathrm{sin}\left(2\pi t\right)+X\left(i,3\right)\mathrm{cos}\left(2\pi t\right)+\dots$

andrewsplot treats NaN values in X as missing values and ignores the corresponding rows.

andrewsplot(X,...,'Standardize',standopt) creates an Andrews plot where standopt is one of the following:

• 'on' — scales each column of X to have mean 0 and standard deviation 1 before making the plot.

• 'PCA' — creates an Andrews plot from the principal component scores of X, in order of decreasing eigenvalue. (See pca.)

• 'PCAStd' — creates an Andrews plot using the standardized principal component scores. (See pca.)

andrewsplot(X,...,'Quantile',alpha) plots only the median and the alpha and (1 – alpha) quantiles of f(t) at each value of t. This is useful if X contains many observations.

andrewsplot(X,...,'Group',group) plots the data in different groups with different colors. Groups are defined by group, a numeric array containing a group index for each observation. group can also be a categorical array, character matrix, string array, or cell array of character vectors containing a group name for each observation.

andrewsplot(X,...,'PropName',PropVal,...) sets optional Line object properties to the specified values for all Line objects created by andrewsplot. (See Line Properties.)

h = andrewsplot(X,...) returns a column vector of handles to the Line objects created by andrewsplot, one handle per row of X. If you use the 'Quantile' input parameter, h contains one handle for each of the three Line objects created. If you use both the 'Quantile' and the 'Group' input parameters, h contains three handles for each group.

## Examples

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This example shows how to create an Andrews plot to visualize grouped sample data.

Create an Andrews plot, grouping the sample data by species.

andrewsplot(meas,'group',species)

Create a second, simplified Andrews plot that only displays the median and quartiles of each group.

andrewsplot(meas,'group',species,'quantile',.25)