# Create a scatter plot matrix in Scilab

## Abstract

In this page, we present a function to create a scatter plot matrix in Scilab.

## Introduction

According to NIST [1], *"given a set of variables X1, X2, ... , Xk, the scatter plot matrix contains all the pairwise scatter plots of the variables on a single page in a matrix format. That is, if there are k variables, the scatter plot matrix will have k rows and k columns and the ith row and jth column of this matrix is a plot of Xi versus Xj."*

This feature is available from the "plotmatrix" function in Stixbox, v2.2. To install it, please use

atomsInstall('stixbox')

and restart Scilab.

The scripts are also available in attachement :

## Scatter plot matrix

The function scattermatrix creates a scatter plot matrix. It has the calling sequence:

scattermatrix(x)

where x is a n-by-ninput matrix of doubles. Here, ninput is the number of input parameters and n is the number of experiments.

Here is the simplest example of scattermatrix. We have a model with 3 inputs and 3 outputs. We are interested in the scatter plot matrix of the outputs y1, y2, y3.

m=1000; x1=grand(m,1,"def"); x2=grand(m,1,"def"); x3=grand(m,1,"def"); y1=2*x1.*x2+x3; y2=-3*x1+x2.^2-2*x3; y3=sin(x1)-3*x2+3*x3; y=[y1,y2,y3]; // ylabels=["Y1","Y2","Y3"]; // No labels scattermatrix(y);

It is straightforward to add labels:

// With labels scattermatrix(y,"xlabels",ylabels);

We can also replace the empty diagonal with an histogram.

// With the histogram scattermatrix(y,"histogram",%t);

## Scatter matrix X vs Y

The function scattermatrixXY plots the dependencies between Y and X in a model.

The script:

m=1000; x1=grand(m,1,"def"); x2=grand(m,1,"def"); x3=grand(m,1,"def"); y1=2*x1.*x2+x3; y2=-3*x1+x2.^2-2*x3; y3=sin(x1)-3*x2+3*x3; x=[x1,x2,x3]; y=[y1,y2,y3]; // xlabels=["X1","X2","X3"]; ylabels=["Y1","Y2","Y3"]; // No labels scattermatrixXY(x,y);

produces:

This is perhaps clearer with labels.

// With labels scattermatrixXY(x,y,"xlabels",xlabels,"ylabels",ylabels);

We can customize various settings, including the labels, the dot symbol and the size of the point.

## References

Author: MichaĆ«l Baudin, 2013