Why does gradient function calculates wrong dimensions?
1 vue (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Michael Mauersberger
le 30 Avr 2020
Commenté : Michael Mauersberger
le 30 Avr 2020
Hi there,
Why does the gradient function calculates the first two dimensions wrong?
Example:
[mshx,mshy,mshz] = ndgrid(0:.1:10,0:.1:10,0:.1:10);
[gxx,gyx,gzx] = gradient(mshx);
[gxy,gyy,gzy] = gradient(mshy);
[gxz,gyz,gzz] = gradient(mshz);
Here all gij are zero except for gyx, gxy, gzz. But how can I calculate the gradient more consistently so that all gij are zero except for gxx, gyy, gzz?
Thank you for your help.
Best regards
Michael
0 commentaires
Réponse acceptée
Ameer Hamza
le 30 Avr 2020
Modifié(e) : Ameer Hamza
le 30 Avr 2020
Use meshgrid instead of ndgrid
[mshx,mshy,mshz] = meshgrid(0:.1:10,0:.1:10,0:.1:10);
[gxx,gyx,gzx] = gradient(mshx);
[gxy,gyy,gzy] = gradient(mshy);
[gxz,gyz,gzz] = gradient(mshz);
3 commentaires
Stephen23
le 30 Avr 2020
Modifié(e) : Stephen23
le 30 Avr 2020
Note that using meshgrid is not a general solution, it fails for N==1, i.e. when the input is a vector:
>> mshx = meshgrid(0:10);
>> gradient(mshx) % oops!
ans =
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1
It could be made to work by providing the first input argument as a scalar and the second as the vector, but that requires special-case handling. This is not just a theoretical problem: it will be relevant if you write a general solution for any N, e.g. with comma-separated lists as to provide the inputs/outputs of the gridding function and calling gradient in a loop on the outputs.
The solution I gave in my answer to your other (identical) question works for all N, no special cases.
Plus de réponses (0)
Voir également
Catégories
En savoir plus sur Creating and Concatenating Matrices dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!