MATLAB: How to weight the marker size in gscatter

gscatterweights

Hello,

I'm using gscatter to plot data by group. I have two vectors of size 100×1 that contain the x and y value, called x and y. I also have a vector of the same size, w, that contains weights. Now, I'd like to weigh the scatter dots by this matrix w. I tried something like

h = gscatter(x,y,gr,linspecer(length(b)-1),'.',30);
h.MarkerSize = w*30;

but it looks like Matlab only accepts a scalar for the marker size.

Thanks for your help.

Best Answer

gscatter() creates lines, and lines can only have one marker size per line.

Consider using multiple scatter() calls instead, one per group (because scatter can only handle one marker shape per call)

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MATLAB: How to label symbols and colors of markers in scatter (example)

create additional objects with position nan and the attributes you want in the legend , and legend() the handles for those specifically .

MATLAB: How to make the plot transparent in a gscattter

Setting transparency of markers with gscatter is not possible as of r2020a.

Update: See Yair's method of setting gscatter marker transparency using undocumented features.

Workarounds

You could use scatter() which does support transparency. Here's one way to translate a gscatter syntax to scatter syntax using arrayfun.

% gscatter syntax
gscatter(x,y,g)
% scatter syntax 
cla()
hold on % important

uniqueGroups = unique(group);
h = arrayfun(@(g)scatter(x(group==g), y(group==g), 'filled'), uniqueGroups);
set(h, 'MarkerFaceAlpha', 0.6) % set transparency level

% scatter syntax specifying color, marker, and size
colors = 'rb';
markers = '^v';
uniqueGroups = unique(group);
cla()
hold on % important
h = arrayfun(@(g)scatter(x(group==g), y(group==g), ...
    100, colors(g), 'filled', 'Marker', markers(g)), uniqueGroups);
set(h, 'MarkerFaceAlpha', 0.4, 'MarkerEdgeColor', 'k', 'MarkerEdgeAlpha',  .2) % set transparency level

Alternatively, you could use gscatter without filled markers.

h = gscatter(x,y,g,colors,'os',10);
set(h,'LineWidth',1)

Why transparency in gscatter doesn't work

The scatter function creates scatter objects. Scatter objects have MarkerFaceAlpha and MarkerEdgeAlpha properties that allow you to set transparency levels.

The gscatter function creates line objects. Line objects do not have these properties. Furthermore, an undocumented method of adding transparancy to some graphics objects by adding a 4th element (0:1) to the RGB color definition does not work with gscatter.

Best Answer

Related Solutions

MATLAB: How to label symbols and colors of markers in scatter (example)

MATLAB: How to make the plot transparent in a gscattter

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