Build colormap with custom colors

I want to be able to create a simple xy plot, with colors representing the frequency of certain values in my data. My y's will be 1,2,3,4,5... etc. My x's will be a wide array of numbers. I want to be able to show by color how often certain ranges within the x values show up (red for more frequent values, blue for less frequent values). Any help would be greatly appreciated.

[Renee Arias]

I really would like to generate a figure like this. Is that still possible with scatter() ?

Answer 1

[Image Analyst]

Use scatter() - with that function you can control the color and size of every marker.

[Image Analyst]

No, for that kind of image you need to use image() or imshow() and then apply a colormap, such as

imshow(grayImage, []);
colormap(jet(256));