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How do I vary color along a 2D line?

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Kathryn McCormick
Kathryn McCormick on 8 Apr 2011
Edited: Roy Goodman on 17 May 2021
I am plotting the x,y position of a point over time. I have the data in two vectors, xpos and ypos, and I plot the path of this point using plot(xpos,ypos).
I would like to have this line change color gradually, representing the time axis ( or the index of the x, y vectors).
Is there an easy way to do this?
  1 Comment
Rajiv
Rajiv on 10 Feb 2014
Can be show line plot with different color, if not to use the surface plot as Matt did.

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Accepted Answer

Matt Fig
Matt Fig on 8 Apr 2011
This is one of the classic 'tricks' of MATLAB graphics.
x = 0:.05:2*pi;
y = sin(x);
z = zeros(size(x));
col = x; % This is the color, vary with x in this case.
surface([x;x],[y;y],[z;z],[col;col],...
'facecol','no',...
'edgecol','interp',...
'linew',2);
EDIT
Changed edgecolor to interp and linewidth to 2. This looks less ragged on my machine.
  11 Comments
Roy Goodman
Roy Goodman on 17 May 2021
I tried this for something I'm working on, and am getting a weird artifact:
Each of the 6 edges of this tetrahedron are computed using the line
surface([x1 x1]',[x2 x2]',[x3 x3]',[y y]',...
'facecolor','none','edgecolor','interp','linewidth',6);
where the arrays x1, x2, x3 parameterize a straight line in 3D space, and y is constant on three of the edges and a monotonically varying sigmoidal function on the other three edges. As you can see from this image, the color index looks very non-monotonic and even noisy on the three edges where the solution varies.
The included graphic was created using the print command, but this is how it appears on the screen as well.
I've tried a few tricks to fix it, neither of which helped
  • reducing the number of colors in the colormap
  • changing the 'edgecolor' to 'flat'

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More Answers (2)

Daniel Refy
Daniel Refy on 7 Mar 2015
N=1 numel(data(:,1)) for a=1:N:numel(data(:,1))-N plot(data(a:a+N,1),data(a:a+N,2),'.','Color',[(a/numel(data(:,1))),0,0] ) hold on end
this will change color of the line from black to red
  1 Comment
Ariel Szklanny
Ariel Szklanny on 2 Dec 2018
This worked great for me, thanks!

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Paulo Silva
Paulo Silva on 8 Apr 2011
Something similar to this:
plot(xpos(1:10),ypos(1:10)) %first points in blue
plot(xpos(11:20),ypos(11:20),'g') %green ones
plot(xpos(21:end),ypos(21:end),'r') %final points in red
another way, the hold all function makes the plots with different color (until the list of available colors ends and after it start from the first one again)
clf
hold all
plot(xpos(1:10),ypos(1:10))
plot(xpos(11:20),ypos(11:20))
plot(xpos(21:31),ypos(21:31))
... %more plots until the end of the indexes
You can insert the code inside a for loop
clf
hold all
N=7; %every N points change color
for a=1:N:numel(xpos)-N
plot(xpos(a:a+N),ypos(a:a+N))
end
  2 Comments
Paulo Silva
Paulo Silva on 8 Apr 2011
You can change the order of the colors and give the impression of it being continously.
axes
MyColorOrder=get(gca,'ColorOrder'); %RGB combinations per row
%make your own color order, you can even add more row (more possible colors)
set(gca,'ColorOrder',MyColorOrder); %RGB combinations per row
hold all
N=7; %every N points change color
for a=1:N:numel(xpos)-N
plot(xpos(a:a+N),ypos(a:a+N))
end

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