Plotting Grayscale from .csv with colorbar restriction

Hi there,

Can anyone please help..? I have grayscale image data in a .csv file I need to plot. The values in the .csv are the z values that I wish to plot as an image, the x and y coordinates of the z values in the file represent the location of that pixel in the image.

I need to restrict the colorbar to say 0 to 0.5 to see the detail in the certain part of the image. Everything below 0 can be black, above 0.5 can be white, but I need 0-0.5 to be greyscale.

I have plotted using the following code but what I get is a mostly blank image.

Please can someone help? I attach the data and my plot.

filename = 'C:\\my data.csv';
M = csvread(filename)
J = contourf(M)
colormap gray
h = colorbar;
set(h, 'ylim', [0 0.5])

Answer 1

[Jaslyn Tan]

In the end I used this:

filename = 'C:\\my data.csv';
M = csvread(filename)
clims = [0 1];
J = imagesc(M,clims)
colormap('jet')

Thank you so much for your help!

Answer 2

[Walter Roberson]

caxis([0 0.5])

[Jaslyn Tan]

Thank you so much! But

filename = 'C:\\my data.csv';
M = csvread(filename)
J = contourf(M)
colormap gray
caxis([0 0.5])

only changes the scale bar, the image is still all black. Am I doing this wrong..? Thank you in advance.