How do I convert g into a double then store it in a new variable then rescale the image with new values that range from 0 to 1 and then plot it?

Answer 1

[Image Analyst]

Try this:

g2 = mat2gray(g);

I don't know what it means to "plot" an image, but if you want to "display" it, use imshow():

imshow(g2, []);