[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## Re: How to use a returning vector function inside another returning vect

**From**: |
Colin Macdonald |

**Subject**: |
Re: How to use a returning vector function inside another returning vector function ? |

**Date**: |
Mon, 31 Jul 2017 10:42:15 -0700 |

**User-agent**: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |

On 2017-07-31 07:54 AM, Adhanedhel wrote:

Norm = norm((G(x+epsi*dx,z)-G(x-epsi*dx,z))/(2*epsi) -
dG(x,z)*dx)

At the end of this line, dG and dx are both vectors so "*" gives an error.

`Perhaps you mean "norm(dG(...))*norm(dx)"? Or an inner product like
``"(dG')*dx", or "dot(dG, dx)", or ... etc
`

`To me, it looks like you are trying to compare the finite difference to
``the directional derivative. One approach:
`
dirderiv = ... % exercise for reader
finitediff = G(x+epsi*dx,z)-G(x-epsi*dx,z))/(2*epsi);
Norm = norm(finitediff) - norm(dirderiv)
best,
Colin