Drawnow without displaying all calculation results in command window

Hello,

I would like to know how can I use the DRAWNOW function more efficiently. I have a GUI with few axes there, and pressing a pushbutton starts calculations. At the end of these calculations (which involves a FOR loop as the main driven parameter), I am plotting the results which are matrices (eg. a pressure matrix VS time matrix plot).

However I would like to plot that in real time, but using the DRAWNOW function just before the end of the FOR loop is too slow:

for(i:0,0.01,100)

% My calculations here

axes(handles.axes26);
plot(timeM, pressureM, '-r');
grid on;
hold on;
plot(timeM, torqueM);
axes(handles.axes28);
plot(timeM, lengthM);
grid on;
axes(handles.axes25);
plot(timeM, sratioM);
axes(handles.axes29);
plot(timeM, alphaM);
drawnow;
end

Is there a more efficient and faster way to plot this in real time?

Answer 1

[Orion]

Hi,

You should decompose your code in 2 part. 1st part : create the graphic objcet at the first iteration 2nd part : update them after.

The creation of graphic object takes time. in your code, you are recreating all your graphics at each iteration.

do something like

for i=0:0.01:100
      % My calculations here

      if i==0
          %%creation of the plot at the 1st iteration
          axes(handles.axes26);
          Hdl.pressureM = plot(timeM, pressureM, '-r');
          grid on;
          hold on;
          Hdl.torqueM = plot(timeM, torqueM);
          axes(handles.axes28);
          Hdl.lengthM = plot(timeM, lengthM);
          grid on;
          axes(handles.axes25);
          Hdl.sratioM =  plot(timeM, sratioM);
          axes(handles.axes29);
          Hdl.alphaM = plot(timeM, alphaM);
      else
          %%update your plot at all other iterations
          set(Hdl.pressureM,'Xdata',timeM,'Ydata',pressureM);
          set(Hdl.torqueM,'Xdata',timeM,'Ydata',torqueM);
          set(Hdl.lengthM,'Xdata',timeM,'Ydata',lengthM);
          set(Hdl.sratioM,'Xdata',timeM,'Ydata',sratioM);
          set(Hdl.alphaM,'Xdata',timeM,'Ydata',alphaM);
      end
  end

Answer 2

[Matt]

Thank you for your answer!

It did the trick, I added a DRAWNOW at the end of the ELSE loop and it plots everything in real time at a reasonable speed. On a side note, it takes about 10 seconds to plot 0.1s of data, even tho the CPU usage is not 100%. Oh well I think I have to simplify my calculations a bit.

[Orion]

you don't have to plot at each iteration.

add a counter to plot at every 20 (change the value if you want) iteration.

count = 0;
for i=0:0.01:100
    % My calculations here

      % update the counter
      count = count + 1;
      if i==0
          %%creation of the plot at the 1st iteration
          axes(handles.axes26);
          Hdl.pressureM = plot(timeM, pressureM, '-r');
          grid on;
          hold on;
          Hdl.torqueM = plot(timeM, torqueM);
          axes(handles.axes28);
          Hdl.lengthM = plot(timeM, lengthM);
          grid on;
          axes(handles.axes25);
          Hdl.sratioM =  plot(timeM, sratioM);
          axes(handles.axes29);
          Hdl.alphaM = plot(timeM, alphaM);
      else
          if count == 20
              count = 0;
              %%update your plot at all other iterations
              set(Hdl.pressureM,'Xdata',timeM,'Ydata',pressureM);
              set(Hdl.torqueM,'Xdata',timeM,'Ydata',torqueM);
              set(Hdl.lengthM,'Xdata',timeM,'Ydata',lengthM);
              set(Hdl.sratioM,'Xdata',timeM,'Ydata',sratioM);
              set(Hdl.alphaM,'Xdata',timeM,'Ydata',alphaM);
          end
      end
  end

Answer 3

[Matt]

Excellent, that is much better, again, thank you very much. I really like MATLAB and its community, you learn everyday!