On the construction of a nonlinear operator

[Calin Gheorghiu]

Dear all,

I try the following:
pdefun = @(u)  -3*(u.^2).*diff(u)-ep*diff((u^3)*diff(u,3)) and I get the error:

Undefined function 'mpower' for input arguments of type 'chebdouble'.

Error in @(u)-3*(u.^2).*diff(u)-ep*diff((u^3)*diff(u,3))

When I try the "correct" form of this pdefun, i.e.,:

pdefun = @(u)  -diff(u.^3-ep*(u.^3).*diff(u,3))

I get the error:
Error using  -
Matrix dimensions must agree.

I can't figure out where the mistake is. Any suggestions is welcome and highly appreciated.

Best,

Calin

Dr. C. I. Gheorghiu

Senior research fellow
"T. Popoviciu" Institute of Numerical Analysis
P. O. Box 68-1
401010 Cluj-Napoca 
Romania
Phone +40 (0)744 70 18 96

http://www.ictp.acad.ro/gheorghiu

https://www.springer.com/gp/book/9783319062297