help required using colormap function in matlab
显示 更早的评论
Hello Everyone,
I am using surf function to plot a 2D matrix Z. The matrix has 61 rows and 98 columns. The data varies from 26.5 to 33.5 , and in few places I have some zeros. Till now i was using the default colourmap for plotting my data using surf command. But now I want more control over the colour pattern. I was reading through the documentation of colormap. It says that
"Specify an array of color data that is equal in size to the z- data and is used for indexed colors"
I create a matrix C of same size as Z but I still did not understand what values to put so that I can use the surf function as
figure(),surf(Z,C)
采纳的回答
Daniel Shub
2013-7-22
It is not clear what you are trying to do. In the simplest case you might be trying to do
Z = 7*rand(61,98)+26.5;
C = ndgrid(1:size(Z,1), 1:size(Z,2));
but I suspect you are trying to change the colormap
set(gcf, 'ColorMap', [1:64; 64:-1:1; [32:-1:1, 64:-1:33]]'/64)
colorbar
4 个评论
Ricky
2013-7-22
Daniel Shub
2013-7-22
The [1:64; 64:-1:1; [32:-1:1, 64:-1:33]]'/64 makes a 64x3 matrix with values between 0 and 1 for use as a color map. Each row corresponds to an RGB value. The set(gcf, 'ColorMap', ... tells MATLAB to use that colormap for the current figure (gcf). The color map maps the z value from (x,y,z) space to a color. MATLAB automatically scales the map to match the range of the data. So in the case of surf(Z), 26.5 corresponds to green and 33.5 corresponds to pink.
Ricky
2013-7-22
Daniel Shub
2013-7-23
A 61x98 matrix is not a color map. A color map must be Nx3 where the three values in each row represents a RGB values. I chose N to be 64 since 64 different colors tends to be enough to be percieved as visually continuous. If you have discrete data with only 8 values, then you could set N to be 8.
In surf(Z) MATLAB plots a 3D surface with the height of the surface defined by Z. It then uses the color map to assign color such that smaller Z have values from the "bottom" of the color map and larger Z have values from the "top" of the map. What those colors are depends on the color map.
In surf(Z,C) Z is still the height, but MATLAB choses the color from the color map based on C.
更多回答（1 个）
Sean de Wolski
2013-7-22
You can modify it interactively by using the colormapeditor
surf(peaks);
colormapeditor
(Also available through: Edit Menu -> Colormap)
类别
在 帮助中心 和 File Exchange 中查找有关 Color and Styling 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
