Speed up coloring segments of a spline curve?
colors, matlab, matlab-figure, plot
Solution
No explicit benchmarks per se, but you can vectorise this easily by a. collecting the plotted points and dividing them into 'segments' (e.g. using the `buffer` function) b. setting the `'color'` property of the Children (thanks to @Suever for pointing out this can be done on an array of object handles directly)
%% Get spline curve
x = [0.16; 0.15; 0.25; 0.48; 0.67];
y = [0.77; 0.55; 0.39; 0.22; 0.21];
spcv = cscvn ([x, y].');
%% Split into segments
pts = fnplt (spcv); xpts = pts(1,:).'; ypts = pts(2,:).';
idx = buffer ([1 : length(xpts)]', 10, 1, 'nodelay'); % 10pt segments
lastidx=idx(:,end); lastidx(lastidx==0)=[]; idx(:,end)=[]; % correct last segment
% Plot segments
plot (xpts(idx), ypts(idx), xpts(lastidx), ypts(lastidx), 'linewidth', 10);
% Adjust colour and transparency
Children = flipud (get (gca, 'children'));
Colours = hsv (size (Children, 1)); % generate from colourmap
Alphas = linspace (0, 1, length (Children)).'; % for example
set (Children, {'color'}, num2cell([Colours, Alphas],2));
Note: As also pointed out in the comments section (thanks @Dev-iL), setting the colour to an RGBA quadruplet the way you ask (i.e. as opposed to a simple RGB triplet) is a newer (also, for now, undocumented) Matlab feature. This code, e.g. will not work in 2013b.
Problem
I am trying to color segments of a spline curve with different RGB values. Many thanks to @Suever, I have a working version: ``` x = [0.16;0.15;0.25;0.48;0.67]; y = [0.77;0.55;0.39;0.22;0.21]; spcv = cscvn([x, y].'); % spline curve N = size(x, 1); figure; hold on; for idx = 1:N-2 before = get(gca, 'children'); % before plotting this segment fnplt(spcv, spcv.breaks([idx, idx+1]), 2); after = get(gca, 'children'); % after plotting this segment new = setdiff(after, before); set(new, 'Color', [idx/N, 1-idx/N, 0, idx/N]); % set new segment to a specific RGBA color end hold off; ``` Now I am looking to speed it up. Is it possible?