corrplot is part of the Econometrics Toolbox. Run this command to determine if you have the Econometrics Toolbox installed on your machine. It returns true (1) or false (0).
license('test','econometrics_toolbox')
Alternative
plotmatrix() is quite similar and with just a few additional lines, you can recreate most of the corrplot().
Here's a demo.
% Load data
load('carsmall')
% Unlike corrplot, plotmatrix cannot receive a table.
% Form a matrix of variables in each column.
data = [Horsepower, Weight, Acceleration, MPG];
nVars = size(data,2);
% Remove any rows that contain NaN values. Otherwise corr() will
% return NaN.
data(any(isnan(data),2), :) = [];
% Create plotmatrix
figure('Name', 'carsmall_data')
[sh, ax, ~, hh] = plotmatrix(data);
% Add axis labels
arrayfun(@(h,lab)ylabel(h,lab),ax(:,1), {'Horsepower','Weight','Accel.','MPG'}')
arrayfun(@(h,lab)xlabel(h,lab),ax(end,:), {'Horsepower','Weight','Accel.','MPG'})
% Compute correlation for each scatter plot axis
[r,p] = arrayfun(@(h)corr(h.Children.XData(:),h.Children.YData(:)),ax(~eye(nVars)));
% Label the correlation and p values
arrayfun(@(h,r,p)text(h,min(xlim(h))+range(xlim(h))*.05,max(ylim(h)),...
sprintf('r=%.2f, p=%.3f',r,p),'Horiz','Left','Vert','top','FontSize',8,'Color','r'),...
ax(~eye(nVars)),r,p)
% Change marker appearance
set(sh, 'Marker', 'o','MarkerSize', 2, 'MarkerEdgeColor', ax(1).ColorOrder(1,:))
lsh = arrayfun(@(h)lsline(h),ax(~eye(nVars)));
% Add least square regression line.
set(lsh,'color', 'm')
