Saving a functiong graph inside a matrix

I am working on edge detection algorithms and i need to produce matrices which cointain graphs of various functions. They need to be in black-white format (no RGB three layer matrices).

For example if i use linspace and build up the graph of y=x^2 how do i save the plot in a non RGB matrix ?

Answer 1

[Dave B]

You can use im2gray to convert an RGB matrix to grayscale:

x = linspace(-5,5,100);
y = x.^2;
plot(x,y)
fr=getframe(gca);

gray_image=im2gray(fr.cdata);

[Andrea Baleani]

thanks, it works!