Content-type: text/html Manpage of rmsfit

rmsfit

Section: User Commands (1)
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NAME

rmsfit - Non-linear Least Squares Fitting  

PERSON RESPONSIBLE

mchw  

CATEGORIES

misc, utility  

DESCRIPTION

RMSFIT is a task that fits one of the following functions with up to 6 parameters (a,b,c,..) to a table of values.

  The first three functions use fixed column numbers:

  1. Phase Structure Function.
          z = a * x**b * sin(y)**c + d
  For the task ATMOS. x, y and z are in column 5, 6 and 8 resp.

  2.      z = a * x**b + c * y
  x, y, and z in column 5, 4, and 8

  3.      z = a * x**2 + b * x + c
  x, z in column 1 and 2 respectively.

  The column numbers must be specified for following functions:
  Lines that begin with '#' are ignored. Giberish can appear in
  unused columns. Columns are separated by blanks.
  The maximum line length is 320 characters.
  Column numbers for x, y, and z specified below.

  4.      z = a * x**b + c

  5.      z = a + b * x + c * x**2 + d * x**3

  6. Comet model radial profile of surface density (brightness)
          z = a/x * integral{exp[-x/b sec(theta)]} theta= -pi/2 to pi/2

  7. Atmospheric opacity:
          z = a + b*(1-exp(-c*x))  ! Tb = Trx + Tsky(1-exp(-airmass*tau0))

  8. Drift scan analysis
          z = a * (exp(-b*(x-c)**2) - exp(-b*(x-d)**2))

  9. Primary beam pattern polynomial fit.
          z = 1 + a1*x**2 + a2*x**4 + ...         "x" is in units of arcmin*GHz.

  10. Primary beam pattern inverse polynomial fit.
          z = 1/(1 + a1*x**2 + a2*x**4 + ... )     "x" is in units of arcmin*GHz.

  11. Primary beam pattern cos**6 fit.
          z = a1*cos(x)**6  "x" is in units of arcmin*GHz.

  12. line length fit:
          z = a1*cos(2pi*a2*x + a3)  "x" is in MHz, a1 is amplitude, 
          a2 is the line length in microsec, and a3 is the phase offset.
 

PARAMETERS

opt
specifies which function is to be fitted. Default opt=1.
col
column numbers for x, y, z variables. Three values. Default=0,0,0 Setting a column number = 0, sets the corresponding variable=1, and modifies the equation accordingly.
in
Input ascii file with columns of data. No default.
npts
Select the first ``npts'' from the input file. Default reads the whole file or 2000 which is the maximum allowed.
par
Initial estimates for parameters (a,b,c,..).
  An initial guess must be specified for each parameter used.
  Default=0,0,0,0,0,0 may not be a good starting guess.
nfit
Number of paramters to fit. Counts from a,b,c,d onwards, e.g. nfit=3 would only fit a,b,c and leave d fixed. Default: 2
log
Output logfile. It will contain the results, a histogram with residuals and all selected measurements, the fit, and residuals. Default: print results and histogram only to terminal.


 

Index

NAME
PERSON RESPONSIBLE
CATEGORIES
DESCRIPTION
PARAMETERS

This document was created by man2html, using the manual pages.
Time: 18:35:38 GMT, July 05, 2011