matlab - Plot (x,y,z) triplets over coordinates (x,y) with color z

Question

I've got a list of points (x,y,z) and would like to visualize them as a curve on a plane with points on (x,y) and any of color/intensity/thickness as z. How can this be done in Matlab?

plot(x,y) gets the right shape, but I need the color to depend on z.

Answer 1

Assuming you don't care about the color of the actual line, but the markers. Use plot in combination with scatter.

Imagine following example data:

t = 0:pi/20:2*pi;
x = sin(t);
y = cos(t);
z = t;

plot3(x,y,z);

Plotted in the 2D-plane:

plot(x,y); hold on
scatter(x,y,300,z); hold off

results in:

From your comment: if you have enough data and you don't need the line, just use scatter, it's exactly what you need.

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Another possibility inspired by a solution on MATLAB Central, considering both line and markers.

surface([x;x],[y;y],zeros(2,length(t)),[z;z],'EdgeColor','flat',...
        'Marker','o','MarkerSize',10,'MarkerFaceColor','flat');

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Make the color dependent on z is quite easy, for changing marker sizes you definitely need the scatter function:

surface([x;x],[y;y],zeros(2,length(t)),[z;z],'EdgeColor','flat'); hold on
MarkerSize = round(z*1000)+1;
scatter(x,y,MarkerSize,z,'.','MarkerFaceColor','auto'); hold off

For on z depending, increasing transparency it's a little tricky. You can find a workaround here, using the patch function.