[Help-gsl] Numeric Problem and splines,

[Cristobal Navarro]

Hello,

i am having a problem, i am not a pro in numerical computation so any
help is welcome to solve my situation here.
i have this Z(v) Function:
http://dl.dropbox.com/u/6380744/img/zfunction.png

and i need to compute U(v):

U(v) = (1+v)* d[ log(Z) ] / dv,   in the range  v [-1.0, 0.0]

for small problems, we can compute U symbolically with Mathematica,
and the result is:
http://dl.dropbox.com/u/6380744/img/ufunction.png

However, when i compute U with gsl_spline using gsl_interp_cspline,
and gsl_spline_eval_deriv
i get different values near v=-1.0
http://dl.dropbox.com/u/6380744/img/uNumeric.png

i know that the problem comes because log(Z) diverges at v=-1.0, and
numerically this is a problem.
 however when multiplied by (1+v), analitically the result is like the
first U i showed solved in mathematica.
A lot of further work depends on U, and when we deal with bigger
problems, the numerical way will be our only solution.

is there a way to solve this problem with the GSL capabilities??
any help is welcome, really!