Curl function outputting -inf and NaN

Hello All,

I have a 2-D velocity field I am trying to calculate the curl of. My input

curlX=curl(Y,Z,V,W);

and it gives me a matrix of a bunch of -inf, inf and NaN.

if I input just curlX=curl(V,W) then it gives me a result for curl but not on the correct coordinate system. Can someone please help me with this?

-Spencer

[Robert]

Try curlX=curl(Y.',Z.',V.',W.');

Answer 1

[Andrew Newell]

If quiver works but not curl, your coordinates may not have the correct form. They have to be monotonic, as if set up by meshgrid.

[Spencer]

Thank you andrew. After you said this I went back and made a meshgrid instead of using the given grid and it now works fine. Thanks!

Answer 2

[Sean de Wolski]

Apparently you're dividing a positive number by zero (inf), a negative number by zero (-inf) and zero by zero (nan). What does your data look like?

Answer 3

[Spencer]

My data consists of 4 40*40 matrices, each matrix representing the Y, Z, V, or W coordinates and velocities respectively.. I dont know exactly what the curl function in matlab does, so I may need to look into it.

Another note: when I use quiver(YY,ZZ,VV,WW) it outputs my velocity field as it should be. So it seems like my matrices are OK.

[Andrew Newell]

Extra details for your question should be included as comments (like this one) or edits to your original question.

Answer 4

[Spencer]

some of my data is very small velocities i.e. e^-4, could this be the reason I am getting these small numbers, is the program carrying the small decimal places?

[Sean de Wolski]

MATLAB works in double precision so it shouldn't have issues at 1e4. Unless you're dividing a very large number by 1e4.

Even:

2e200/1e4

doesn't go to inf.