Problem with plotting vector fields

Question

Randy Chen 2020-10-13

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评论： Randy Chen 2020-10-14

I keep getting this error while trying to plot a vector field:

[X,Y] = meshgrid(2:10,2:10);
U = X/(X^2+Y^2);
V = Y/(X^2+Y^2);
quiver(X,Y,U,V,0)
Warning: Matrix is singular to working precision. 
 
Warning: Matrix is singular to working precision. 

I don't understand. What does this mean??

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Randy Chen 2020-10-13

also the figure I get comes out to be emtpy

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Answer 1

Stephen23 2020-10-13

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编辑：Stephen23 2020-10-13

在 MATLAB Online 中打开

"also the figure I get comes out to be emtpy"

You need to use array operations, not matrix operations:

>> [X,Y] = meshgrid(2:10,2:10);
>> U = X./(X.^2+Y.^2); % note array operations ./ and .^
>> V = Y./(X.^2+Y.^2); % note array operations ./ and .^
>> quiver(X,Y,U,V,0)

Tip: if you are not doing linear algebra then most likely you should be using array operations:

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

"I don't understand. What does this mean??"

The matrix operation mrdivide you used by mistake is trying to solve an unsolvable set of equations. The fact that it solves sets of equations is explained in its documentation, which is why you should read the documentation for every operator that you use, no matter how trivial you think it is.