---
name: "fderiv"
section: "3m"
platform: "linux"
package: "iraf"
version: "2.11.3-2"
release: "Debian 3.0 (Woody)"
platforms: ["linux"]
url: "https://new.carta.tech/fderiv"
---

# fderiv(3m)

## NAME

fderiv

## DESCRIPTION

subroutine fderiv.f (non-analytical)

source\
   Bevington, page 242.

purpose\
   evaluate derivatives of function for least-squares search\
     for arbitrary function given by functn

usage\
   call fderiv (x, i, a, deltaa, nterms, deriv)

description of parameters\
   x      - array of data points for independent variable\
   i      - index of data points\
   a      - array of parameters\
   deltaa - array of parameter increments\
   nterms - number of parameters\
   deriv  - derivatives of function

subroutines and function subprograms required\
   functn (x, i, a)\
     evaluates the fitting function for the ith term