Setting graph figure size

 figure (1)
 hFig = figure(1);
 set(gcf,'PaperPositionMode','auto')
 set(hFig, 'Position', [0 0 xwidth ywidth])
 plot(x,y)
 print -depsc2 correlation.eps;       % for saving in eps, look up options for saving as png or other formats you may need

This saves the figure in the dimensions specified

The properties that can be set for a figure is referenced here.

You could then use:

figure_number = 1;
x      = 0;   % Screen position
y      = 0;   % Screen position
width  = 600; % Width of figure
height = 400; % Height of figure (by default in pixels)

figure(figure_number, 'Position', [x y width height]);

Write it as a one-liner:

figure('position', [0, 0, 200, 500])  % create new figure with specified size  

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