Plotting a variable against loop iteration

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I have a variable changing within a loop and I want to plot it against the loop's iteration in real time, sounds simple enough but I just can't get it to work, I get an empty plot with the Y axis changing without having anything plotted.

        for i=900:1:nfiles
       %%Code that generates variable (Y) here %%
        x = linspace(0,nfiles);
        plot(x,Y,'LineWidth',2,...
                'MarkerEdgeColor','b',...
                'MarkerFaceColor','b',...
                'MarkerSize',10);
           drawnow
           end

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Stephen23 2017-8-17

编辑：Stephen23 2017-8-17

How many values of Y are calculated on each iteration? By this description "...the Y axis changing without having anything plotted" it sounds like you are plotting one point at a time.

In any case, the best solution will be to store all of the data in one array and then plot it after the loop.

Alla 2017-8-18

That would definitely work, but what I need is to plot the results in real time.

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Answer 1

Robert U 2017-8-18

在 MATLAB Online 中打开

1 个投票

Hi Alaa MAZOUZ,

The marker-property of plot is by default 'none'. Choose a marker.

x is - according to the presented example - not dependent on i, thus, you do not calculate it repeatedly in every loop.

I like it better to open one parent figure which can be modified and draw the results into it. That might be useful for you, too. You might want to fix the limits of your axes to see Y moving in a fixed frame instead of seeing the frame moving for a quite fixed point (cloud).

 x = linspace(0,nfiles);
 ah = axes; % open parent figure
 for i=900:1:nfiles
  %%Code that generates variable (Y) here %%
  plot(ah,x,Y,'LineWidth',2,...
           'Marker','.',...  % set marker to filled point
           'MarkerEdgeColor','b',...
           'MarkerFaceColor','b',...
           'MarkerSize',10);
  drawnow
 end

Kind regards,

Robert

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Robert U 2017-8-18

在 MATLAB Online 中打开

Example for a point drawing a circle:

 clear
 ah = axes;
 for i = 0:360
    x(i+1) = sind(i);
    Y(i+1) = cosd(i);
    plot(ah,x(1:end-1),Y(1:end-1),...
        'LineWidth',1);
    hold on
    plot(ah,x(end),Y(end),...
        'LineWidth',2,...
        'Marker','.',...
        'MarkerEdgeColor','r',...
        'MarkerFaceColor','r',...
        'MarkerSize',24);
    axis equal
    ah.XLimMode = 'manual';
    ah.XLim     = [-1 1];
    ah.YLimMode = 'manual';
    ah.YLim     = [-1 1];
    hold off
    drawnow;
 end

Alla 2017-8-18

编辑：Alla 2017-8-18

Thank you Robert that was quite helpful, I have managed to make it work but only after I had one other figure that displays other results within the loop omitted, basically when the code switched between the two figures mid loop the plot does not hold on to the plotted points and restarts each time giving me dots,to work around this I have tried to have all of the results displayed in one figure and avoid the switching all together I but couldn't manage that either.

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