Modifying a quiver plot

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Douglas Brenner 2016-10-25

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https://ww2.mathworks.cn/matlabcentral/answers/309147-modifying-a-quiver-plot

评论： Star Strider 2016-10-26

Some of the arrows in my quiver plot are too big. I want to set them to zero using a for loops and a if statement. How do I write the if statement condition? Is there another way to do this? Thanks

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Answer 1

Star Strider 2016-10-25

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The last two arguments to the quiver function are the x- and y-magnitudes of the arrows. If you want to set a length threshold, create a (Nx2) matrix of the magnitudes, use that as an argument to the hypot function (that will calculate the lengths), and then using logical indexing, set the magnitude rows to zeros of the lengths that exceed your desired threshold.

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Star Strider 2016-10-26

Douglas Brenner’s ‘Answer’ moved here —

Don't understand your answer but that may just indicate my ignorance of matlab. In my case the quiver plot comes from the outputs of imgradientxy. Using those I can calculate the length of the vectors and for the ones that exceed a threshold set the components to zero.

Star Strider 2016-10-26

在 MATLAB Online 中打开

I’m describing something like this:

uv = randi(99, 15, 2);                                      % Create ‘u’ and ‘v’ As A Matrix
len = hypot(uv(:,1), uv(:,2));                              % Calculate Lengths
lenv = len > 100;                                           % Logical Vector, Length Threshold = 100
uv(len > 100,:) = repmat([0 0], sum(lenv),1);               % Set ‘uv’ Rows Meeting Criteria To Zeros

That works.

It should be straightforward to make it work with your code.

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