How to subplot 2 constellations with scatterplot (and NOT "scatter plot")

Dear all,

I am trying to plot constellations (numerical communications).

The attached file (test.mat) give 4 matrices: the waveformi with i=1,2,3,4 from which we reconstruct the signal.

I would like to plot in a SAME figure using the built-in function "scatterplot".

How do the trick with the "scatterplot" and subplots built-in functions?

(I want to precise, I DON'T WANT to use "scatter plot"..

I know how to do a "hand-made" scatter plot with real an imaginary parts, but we need to normalise and work the layout by hand...)

Thanks in advance!

The small code is:

% loading the measured data
load test.mat

% reconstruction of the signals
x = waveform1+1i*waveform2;
y = waveform3+1i*waveform4;

% plotting
figure
    subplot(1,2,1)
        scatterplot(x)
    subplot(1,2,2)
        scatterplot(y)

Answer 1

[Voss]

As far as I can tell, there is no way to use scatterplot to create a scatter plot in a subplot (or in any axes other than the one scatterplot creates), but maybe the following approach can work. The idea is to create the scatter plots using the scatterplot function, then copy the graphics objects to a common figure.

% loading the measured data
load test.mat

% reconstruction of the signals
x = waveform1+1i*waveform2;
y = waveform3+1i*waveform4;

% figure where two scatterplots will end up:
f = figure('Color',[0 0 0]);

scatter_fig = scatterplot(x); % create scatterplot
copyobj(get(scatter_fig,'Children'),f); % copy everything from scatterplot figure to f
delete(scatter_fig); % delete scatterplot figure

scatter_fig = scatterplot(y); % create scatterplot
copyobj(get(scatter_fig,'Children'),f); % copy everything from scatterplot figure to f
delete(scatter_fig); % delete scatterplot figure

% re-position the two axes in figure f:
ax = findall(f,'Type','axes');
set(ax(2),'Position',[0.1 0.11 0.38 0.815]);
set(ax(1),'Position',[0.6 0.11 0.38 0.815]);

[Louis Tomczyk]

Hello,

thanks for the reactivity!

It is BRILLIANT!

There might be one thing which can be boring, is to find the exact location values when you want to display more than 2 constellations (for example when you want to show several outputs after several DSP steps).

By "Exact" I mean when we want things to be centered, constant x/y spacing...

However for 2 constellations, the code is PERFECT, thanks again :)

Best,

louis

[Voss]

You're welcome!

I agree the solution I came up with is not very general. However, it's possible to adapt the last part, where the axes' Positions are set:

% re-position the two axes in figure f:
ax = findall(f,'Type','axes');
set(ax(2),'Position',[0.1 0.11 0.38 0.815]);
set(ax(1),'Position',[0.6 0.11 0.38 0.815]);

to handle any number and arrangement of axes, similar to how subplot does it.

[Louis Tomczyk]

Finally I wrote my own function to display the constellations with scatter plot instead as it is easier to set the locations and axis properties to my mind.

It takes varying number of polarisation-multiplexed (or not) signals in argument.

If it can be useful for some.

Thanks again for your help!

Best,

louis