> Is this documented anywhere?
No, the 1x4 RGBA alpha-color option is not documented at this time. One reason is that the alpha channel is not saved when saving and loading the figure. This also poses a problem in live scripts where the alpha value is not preserved. Another issue with partially transparent lines is that if the line width is thick enough, you'll see parts of the line fold over on itself at sharp curves. You can see this by increasing the linewidth in the demo below to something larger like 30.
Line alpha can be achieved by using patch but it's a bit tricky to get the inputs right so here's an anonymous function that's merely a wrapper to this process.
lineAlphaFcn = @(x,y,color,alpha,varargin) ...
patch('XData',[x(:);nan],...
'YData',[y(:);nan],...
'EdgeColor',color,...
'EdgeAlpha',alpha, ...
varargin{:});
x = 0 : .1 : 9;
y = sin(x);
h = lineAlphaFcn(x,y,'b',0.4,'LineWidth',3);
Related topics
- See also this thread that shares this approach and this one that uses datetime values.
- I also used this approach to create this visualization of first 10,000 dp of pi which contains a single "line" (patch).
- Discussion in "ideas" channel.
