Plots via s-function

Hello,

I've written a Level2 S-Function, that plots space vector diagramms during my Simulink simulations. This is working so far, but the problem is that the execution time of the s-function slows down my simulation due to the matlab interpreter.

So my question is, is there any way to create and modify matlab-figures with a mex S-Function? After a lot of searching, I could not find any commands for doing that.

Thank you for your help

Tobias Gemaßmer

Answer 1

[Titus Edelhofer]

Hi Tobias,

hmm, then there is indeed not much more that can be done ... writing the S-function in C will not make much of a difference in this case I guess. You might profile your S-function (just call

profile on

before running the simulation and

profile report

afterwards. The report should show up the time spent in your S-Function. I don't expect much interesting there, but just to be sure ...

Titus

Answer 2

[Titus Edelhofer]

Hi Tobias,

not really. What I would suggest is to reduce the sample time of the output so that the S-function (plotting) is not done every time step but e.g. every 10th step only ...

Second: how does the plotting work, do you redraw the entire plot every time step (plot(x,y)), or (preferably) do you store the handle of the plot in some work vector and do only update the line, something like

set(h, 'xdata', newXData, 'ydata', newYData);

This is usually significantly faster.

Titus

Answer 3

[Tobias Gemaßmer]

Hi Titus

thank you for your answer.

Since the plot is a space-vector-diagram, it consits of a couple of lines. I store the handle of every line in a work vector and update the x and y data. I already reduced the sample time of the S-function, which speeded up the simulation, but for me was kind of dissatisfactory.

Answer 4

[Tobias Gemaßmer]

Hi Titus,

By using the profiler, I recognized, that most of the calculation time is needed on some function according to the legend. So I was able to speed up the update function of my figure by having a static legend using

% Static legend

set(gca,'LegendColorbarListeners',[]);

setappdata(gca,'LegendColorbarManualSpace',1);

setappdata(gca,'LegendColorbarReclaimSpace',1);

(I found those commands on http://undocumentedmatlab.com/blog/plot-performance/)

So anyway, my function doesn't slow down the simulation any more. Thank you for your good advice

Tobias

[Titus Edelhofer]

Good to hear, so I guess the question might be seen as answered ...