Hello, everyone,

Can anyone please help me use subroutine SAVGOL correctly,

in order to get the derivatives of a data set?

The book(Numerical Recipes in Fortran) says SAVGOL gives

convolution coefficients for smoothing or derivatives, according

to the value of variable ld, which is 0 for smoothing and N for

Nth derivative.

I had no problem to smooth a data set with SAVGOL, but

when I tried to get the first derivative of a noise-corrupted

sine wave function(just for test), I couldn’t get a cosine

until I decreased m, the order of smoothing polynomial, down to

2, and the window down to 3 points long, which according to the

authors are not recommended for derivatives.

(I can’t even make it work on a perfect slow sine waveform.)

Any advice will be appreciated.

Thanks in advance.

Jianhong Wang

Univ. of Guelph

Ontario, Canada