Easy Question, update scatter point in loop

Question

Yuang 2014-6-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/137420-easy-question-update-scatter-point-in-loop

评论： Ben11 2014-6-24

Hi:

I just want to get the 4 vectors scatter update every time in my loop. Delete the last time points then plot then hold on to new loop.

How to do that??

Thank you.

x1{1} = [.2; .3]; x2{1} = [.3; .4]; x3{1} = [.5; .6]; x4{1} = [.6; .7]; k = 1;

for k = 1:1:50

    scatter(x1{k}(1,1), x1{k}(2,1));
    hold on
    scatter(x2{k}(1,1), x2{k}(2,1));
    hold on 
    scatter(x3{k}(1,1), x3{k}(2,1));
    hold on
    scatter(x4{k}(1,1), x4{k}(2,1));
    x1{k+1} = (x1{k} + x2{k} + x4{k})/3;
    x2{k+1} = (x1{k} + x2{k} + x3{k})/3;
    x3{k+1} = (x2{k} + x3{k} + x4{k})/3;
    x4{k+1} = (x1{k} + x3{k} + x4{k})/3;
end

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Answer 1

Ben11 2014-6-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/137420-easy-question-update-scatter-point-in-loop#answer_142316

在 MATLAB Online 中打开

What if you try this:

x1{1} = [.2; .3]; x2{1} = [.3; .4]; x3{1} = [.5; .6]; x4{1} = [.6; .7]; k = 1;
figure
for k = 1:1:50
hold all
    scatter(x1{k}(1,1), x1{k}(2,1))
      scatter(x2{k}(1,1), x2{k}(2,1));
      scatter(x3{k}(1,1), x3{k}(2,1));
      scatter(x4{k}(1,1), x4{k}(2,1));
      x1{k+1} = (x1{k} + x2{k} + x4{k})/3;
      x2{k+1} = (x1{k} + x2{k} + x3{k})/3;
      x3{k+1} = (x2{k} + x3{k} + x4{k})/3;
      x4{k+1} = (x1{k} + x3{k} + x4{k})/3;
  hold off
  drawnow
  end

First you create a figure, then you force the plot to update with drawnow. You can keep the original "hold on" calls and see what it does as well.

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Yuang 2014-6-24

Sorry. I mean I want the figure shows the path x1,x2,x3 and x4 go.

Ben11 2014-6-24

在 MATLAB Online 中打开

ok. Do you mean something like this:

for k = 1:50
      scatter(x1{k}(1,1), x1{k}(2,1))
      if k > 1    
          line([x1{k-1}(1,1) x1{k}(1,1)],[x1{k-1}(2,1) x1{k}(2,1)],'Color','r');
      end
      drawnow
      hold on
      scatter(x2{k}(1,1), x2{k}(2,1));
      if k > 1    
          line([x2{k-1}(1,1) x2{k}(1,1)],[x2{k-1}(2,1) x2{k}(2,1)],'Color','g');
      end
      drawnow
      hold on
      scatter(x3{k}(1,1), x3{k}(2,1));
      if k > 1    
          line([x3{k-1}(1,1) x3{k}(1,1)],[x3{k-1}(2,1) x3{k}(2,1)],'Color','b');
      end
      drawnow
      hold on
      scatter(x4{k}(1,1), x4{k}(2,1));
      if k > 1    
          line([x4{k-1}(1,1) x4{k}(1,1)],[x4{k-1}(2,1) x4{k}(2,1)],'Color','k');
      end
      drawnow
      hold on
      x1{k+1} = (x1{k} + x2{k} + x4{k})/3;
      x2{k+1} = (x1{k} + x2{k} + x3{k})/3;
      x3{k+1} = (x2{k} + x3{k} + x4{k})/3;
      x4{k+1} = (x1{k} + x3{k} + x4{k})/3;
  hold off
  pause(.1)
  end

I seems odd is it what you would expect?

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Answer 2

Geoff Hayes 2014-6-24

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https://ww2.mathworks.cn/matlabcentral/answers/137420-easy-question-update-scatter-point-in-loop#answer_142320

在 MATLAB Online 中打开

Try grabbing the handle returned from each scatter call and then deleting that on subsequent iterations. Outside the for loop declare an array to manage the scatter plot handles

 % declare an array for the handles to the scatter plots
 scatterHandles = [];

Now within the for loop, delete the handles if any exist

 for k = 1:1:50
     % delete scatter plot data from previous iteration if it exists
     if ~isempty(scatterHandles)
         for m=1:length(scatterHandles)
             delete(scatterHandles(m));
         end
     end
     % get the scatter plot handles for each call to scatter
      hold on
      scatterHandles (1) = scatter(x1{k}(1,1), x1{k}(2,1));
      scatterHandles (2) = scatter(x2{k}(1,1), x2{k}(2,1));
      scatterHandles (3) = scatter(x3{k}(1,1), x3{k}(2,1));
      scatterHandles (4) = scatter(x4{k}(1,1), x4{k}(2,1));
     % etc.
  end