plot3+color

I have a [N,4] data set which I want to visualize as 3d line representing the fourth column as a color. Any ideas on how to do this?

Answer 1

[Matt Tearle]

Sorry, just noticed this hasn't been answered for some reason. Simplest solution is to make a scatter plot rather than a line plot:

% Make some fake data
x = linspace(0,1);  % x = data(:,1);
y = cos(10*x);      % y = data(:,2);
z = sin(15*x);      % z = data(:,3);
c = x+y-z;          % c = data(:,4);

figure
scatter3(x,y,z,2,c)
colorbar

If, however, you really need lines, you probably need to brute-force it.

figure
cmap = colormap;
% change c into an index into the colormap
% min(c) -> 1, max(c) -> number of colors
c = round(1+(size(cmap,1)-1)*(c - min(c))/(max(c)-min(c)));
% make a blank plot
plot3(x,y,z,'linestyle','none')
% add line segments
for k = 1:(length(x)-1)
    line(x(k:k+1),y(k:k+1),z(k:k+1),'color',cmap(c(k),:))
end
colorbar

Here I'm using the default colormap for the figure to define the colors. You can specify colors however you want, as long as you have a way to index into them.

[Guðmundur]

Excelent solution, I would only like to add a change in the colorbar limits

caxis([ min(c) , max(c)]) % colorbar limits