how do I create a handle to a plot without plotting?

Question

Rick Giovanini 2018-1-9

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回答： Pablo Saavedra G. 2019-2-18

Hello, here is my code

    function handle = DrawLink(z,w,h,handle)
        pts = [z-w/2, z+w/2, z+w/2, z-w/2; 0, 0, h, h];
        X = pts(1,:);
        Y = pts(2,:);
        if isempty(handle)
            handle = fill(X,Y,'b');
        end
    end

I am trying to create a handle to the plot without plotting it while I make it. How do I do this? Thanks.

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Answer 1

Star Strider 2018-1-9

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Try this:

fh = figure(1);
set(fh, 'Visible','off')
plot(rand(1,10), rand(1,10), 'p')

Then later, when you want to see it:

set(fh, 'Visible','on')

and it magickally appears!

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Star Strider 2018-1-9

在 MATLAB Online 中打开

I am not certain what you are doing, or the reason you are passing the handle as an argument and returning it as an output.

I would return the ‘pts’ variable as a separate output, along with ‘handle’, created in the function rather than passed to it. You can set the figure handle to 'Visible','off' inside the function, and then set it to 'Visible','on' outside the function.

In your code, ‘handle’ is to a patch object. Making it invisible with:

set(handle, 'Visible','off')

simply makes the patch object invisible while leaving the figure object unaffected.

Something like this could work:

      function [handle, fh, pts] = DrawLink(z,w,h,handle)
          pts = [z-w/2, z+w/2, z+w/2, z-w/2; 0, 0, h, h];
          X = pts(1,:);
          Y = pts(2,:);
          if isempty(handle)
              fh = figure;
              set(fh, 'Visible','off')
              handle = fill(X,Y,'b');
          end
      end

That returns everything of interest so you can work with it outside your function later.

I am guessing what you are doing, so this is just a suggestion.

Rick Giovanini 2018-1-10

So, I don't want to turn the whole plot off because I have other things that are plotted, and I have these things animated. I just want a handle to this, and then I need to do something to determine if I need to rotate it, and then to plot it, or just plot it first of all. In order to rotate without plotting, I need to have this handle.

Star Strider 2018-1-10

I do not understand what you want to do, or what your requirements are.

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Answer 2

Pablo Saavedra G. 2019-2-18

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You can always create an empty handle at the current axes and pass it to your function, for example:

handle = plot([],[],'-');

then in your function, the line with the if will get a TRUE

if isempty(handle)
    handle = fill(X,Y,'b'); %  note that previous handle (from plot) is repalced to fill
end

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