unexpected matlab operator error when plotting from a simulink matlab function

Hi to everyone,

I have a matlab function called from simulink and I'm trying to plot all the elements of a vector, but unexpected matlab operator error appears.

My aim is to build a vector adding [u,u] at each step (like vector=[vector;x]) and then plot it at the end of each step.

I don't know why it doesn't accept the ":" in the plot.

The code is:

function fcn(u)

coder.extrinsic('evalin', 'assignin', 'plot')

if u==0

xx=[u,u];

assignin('base','xx',xx);

sz=size(xx);

assignin('base','sz',sz);

else

sz=zeros(1,2);

szz=evalin('base','sz');

xx=zeros(szz(1),szz(2));

xxx=evalin('base','xx');

xx=[xxx;[u,u]];

assignin('base','xx',xx);

end

figure(1)

plot(xx(:,1),xx(:,2),'ko');

end

Does anyone know how to fix it?

Thanks!

Answer 1

[Paul]

Hi Edoardo,

Are you really trying to plot u vs. u? Wouldn't that just be a straight line?

If I understand what you're trying to do, would the XY Graph be applicable?

If wanting to do this in a Matlab Function, this code worked for me. It seems simpler and doesn't have to work with the base workspace.

function fcn(t,u)
% Incrementally add points to a line plot of t vs u

persistent init hline
if isempty(init)
    init = 1;
    figure;
    hline = line(gca,t,u);
else

set(hline,'XData',[get(hline,'XData') t]);
set(hline,'YData',[get(hline,'YData') u]);

end

end

[Alberto]

Hi Paul! Thanks! It works! I replaced "line" with "plot" and that's what I wanted to plot!

No, [u,u] was only an example, the vector to add changes at each step, it can be [1,0], [5,8], [4,-7] etc.