Setting 'FaceAlpha'<1 for a patch object causes x- and y- axes of the plot to dissapear. Why and how can this be corrected?

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Anton Semechko 2014-6-24

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https://ww2.mathworks.cn/matlabcentral/answers/137404-setting-facealpha-1-for-a-patch-object-causes-x-and-y-axes-of-the-plot-to-dissapear-why-and-how

评论： Ben11 2014-6-24

Hello everyone,

have any of you ever plotted a 2D patch object and noticed that upon altering its 'FaceAlpha' value below 1, it causes the x- and y-axes of the plot to disappear? Just to clarify, by x- and y- axes I mean the horizontal and vertical lines of the plot, respectively, not the axes object where the patch is plotted.

Here is an example of what I talking about:

% Plot a simple patch object
x=[0 1 1 0 0];
y=[0 0 1 1 0];
figure('color','w')
ha1=subplot(1,2,1);
ha2=subplot(1,2,2)
h=fill(x,y,'g');
% DO the same as above, but alter the FaceAlpha value of the patch
figure('color','w')
ha1=subplot(1,2,1);
ha2=subplot(1,2,2);
h=fill(x,y,'g');
set(h,'FaceAlpha',0.5)

Note that changing the transparency of the patch in the second figure caused the x- and y- axes (i.e., horizontal and vertical lines) to disappear in ha1 and ha2.

Does anyone know why this happens, and how can it be corrected?

Thank you!

PS - Not sure if its relevant, but I am using R2013a version of Matlab.

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Answer 1

Ben11 2014-6-24

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https://ww2.mathworks.cn/matlabcentral/answers/137404-setting-facealpha-1-for-a-patch-object-causes-x-and-y-axes-of-the-plot-to-dissapear-why-and-how#answer_142309

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I changed your code a bit and set the linewidth property to 1.5 (actually any value larger than 1.5 worked) and it seems to be ok. Honestly I tried many things and this works althought I don't really know why. Anyhow here is the code:

% Plot a simple patch object
x=[0 1 1 0];
y=[0 0 1 1];
hfig1 = figure('color','w');
ha1=subplot(1,2,1);
ha2=subplot(1,2,2);
hfill1 = fill(x,y,'g');
hfig2 = figure('color','w');
ha3=subplot(1,2,1);
ha4=subplot(1,2,2);
hpatchobj = patch(x,y,'g','FaceAlpha',0.5);
set(ha3,'LineWidth',1.5);