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Defining value range in colormap manually
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My data range is 0-15
I plotted
scatter(X,Y,Data);
colormap([0 0 0; 1 0 0;0 0 1]);
it takes color 0 0 0 as 0-5 and so on
I need
0 0 0 as <4
1 0 0 as>4 and <9
0 0 1 as >9
How do I define value range in colormap
0 commentaires
Réponse acceptée
Stephen23
le 11 Jan 2016
Modifié(e) : Stephen23
le 11 Jan 2016
You just need to supply the fourth option to scatter, which maps the values onto the colormap. One very easy way to do this is to use histc / histcounts:
X = rand(50,1);
Y = rand(50,1);
data = randi(16,50,1)-1;
[~,C] = histc(data,[0,4,9,Inf]);
scatter(X,Y,10,C)
colormap([0,0,0;1,0,0;0,0,1]);
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/172465/image.png)
7 commentaires
Stephen23
le 12 Jan 2016
My pleasure. You can also Accept answer that best resolve your question. This gives points to those who volunteer to help you.
Hasan Jamil Apon
le 12 Avr 2021
If I want to set color limit for 3D plot,then what sort of changes I have to make? Like I want the red color for the Z axis value between 0.8 to 0.93, cyan color for Z axis value between 0.93 to 0.95, yellow color for Z axis value between 0.95 to 1 for given X and Y values. Please give me some guidance in this issue. Will be really be grateful!
Plus de réponses (1)
Image Analyst
le 11 Jan 2016
I'm not sure what you mean. All of data (if it's a 1-D array) will show up in the same color, and as circles with whatever markersize you specified as Data (which, by the way, I think is a bad name for you to choose as the marker size).
If you want multiple colors, you have to call scatter() twice.
Data = 20; % Circle diameter
% Define sample data.
X = 12 * rand(1,20);
Y = 12 * rand(1,20);
scatter(X,Y,Data);
% Define second sample data.
X = 12 * rand(1,20);
Y = 12 * rand(1,20);
hold on;
scatter(X,Y,Data);
legend('Set #1', 'Set #2');
grid on;
% colormap([0 0 0; 1 0 0;0 0 1]);
If you want, you can pass in an array that is the colormap for markers based on the index.
markerSize = 20; % Circle diameter
% Define sample data.
numPoints = 500;
X = 12 * rand(1, numPoints);
Y = 12 * rand(1, numPoints);
cMap = zeros(length(X), 3);
% Define markers to be red if both X and Y >4 and < 9
red = X > 4 & X < 9 & Y > 4 & Y < 9;
cMap(red, 1) = 1;
% Define markers to be blue if both X and Y >= 9
blue = X >= 9 & Y >= 9;
cMap(blue, 3) = 1;
scatter(X,Y, markerSize, cMap);
grid on;
5 commentaires
Hasan Jamil Apon
le 12 Avr 2021
If I want to set color limit for 3D plot,then what sort of changes I have to make? Like I want the red color for the Z axis value between 0.8 to 0.93, cyan color for Z axis value between 0.93 to 0.95, yellow color for Z axis value between 0.95 to 1 for given X and Y values. Please give me some guidance in this issue. Will be really be grateful!
Image Analyst
le 12 Avr 2021
I'm sure you made the obvious changes (something like)
% Define markers to be red if Z >= 0.8 and Z <= 0.93
redRows = Z >= 0.8 & Z <= 0.93;
cMap(redRows, :) = 1;
% Define markers to be cyan if Z >= 0.93 & Z <= 0.95
cyanRows = Z >= 0.93 & Z <= 0.95;
cMap(cyanRows, :) = [0, 1, 1];
but it didn't work, so you're asking me. I don't know what other changes you made in the code, which you forgot to post. Please post your non-working code along with your XYZ data in a .mat file with the paperclip icon.
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