How to output matrix grayscale?

I am trying to output my matrix grayscale with imshow(), but its looks like gradient.

My code is:

 s=4;
 A=256;
 N=200;
 i=1:N;
 r=0.1*(i-N/2);
 f=exp(-r.^2/2/s^2);
 M=A*(f'*f);
 imshow(M,[]);

Please, help me to find a solution to this problem

[KALYAN ACHARJYA]

"matrix grayscale with imshow(), but its looks like gradient"

Can you re-read the statement again and explain more? graysclae is scale range (shaded variation), where as gradient is derivative?

Answer 1

[KALYAN ACHARJYA]

This one?

imagesc(M);

[Pryschepa Daryna]

That outputs colorful M , but I need to output it grayscale with imshow

[Bjorn Gustavsson]

No, you don't need to use imshow to get the matrix in gray-scale. You can set the colormap to gray. You can also read the help and documentation to imshow to learn how that functions works, particularly with respect to intensity-scaling of inputs with different data-types...

[KALYAN ACHARJYA]

@Pryschepa Daryna set the colormap as you want

https://in.mathworks.com/help/matlab/ref/colormap.html

Answer 2

[Bjorn Gustavsson]

You could use imagesc instead of imshow. Combined with colorbar you get a neat display of your matrix. Since you asked for gray-scale, you'll also have to set the colormap, so something like this:

imagesc(M)
colorbar
colormap(gray)

HTH