How can I make the 'plot' function markers and lines transparent using 'alpha' or otherwise?

I want to make a plot with semi-transparent markers and lines using 'plot' and 'alpha', but it's not working. Why?

Answer 1

[MathWorks Support Team]

Basic 'plot' function markers do not currently support transparency or alpha values. If you would like to make a scatter plot with transparent markers, it is suggested that you use the 'scatter' function and use either 'alpha' or set the value of the property 'MarkerFaceAlpha':

scatter1 = scatter(x,y,'MarkerFaceColor','r','MarkerEdgeColor','k'); 
% Set property MarkerFaceAlpha and MarkerEdgeAlpha to <1.0
scatter1.MarkerFaceAlpha = .2;
scatter1.MarkerEdgeAlpha = .2;

Or:

scatter1 = scatter(x,y,'MarkerFaceColor','r','MarkerEdgeColor','k'); 
alpha(scatter1,.2)

If you would like to have a line plot using 'plot' with transparent markers on top, you can simply use 'hold on/off' and 'scatter' in conjunction for the same desired effect:

plot(x,y);
hold on
scatter1 = scatter(x,y,'MarkerFaceColor','r','MarkerEdgeColor','k'); 
scatter1.MarkerFaceAlpha = .2;
hold off

Please see the "Input Arguments" list for the property 'value' on the documentation page for 'alpha' for a list of graphics objects that support face transparency:

https://www.mathworks.com/help/matlab/ref/alpha.html#buvaucs-5

Answer 2

[Rini Varghese]

not sure if anyone is still following this, but for MATLAB's 'plot' function, color and transparency are specified as a 4 element vector, with the first 3 as rgb and last element as alpha value. For example, following will produce a red line with transparency 0.2.

plot(x,y,'Color'[1, 0, 0, 0.2])

[Rini Varghese]

Right, yes, the 'plot' function won't allow you to change transparency for markers, just lines. One alterrnative is to use the 'scatter' function instead. You can individually specificy edge color, edge alpha, face color, face alpha... Hope this helps.

scatter(x,y,'o','MarkerEdgeAlpha',0.2)