The program fitcheb reads in an input file, basename.inp(.ext), containing the rate coefficient as a function of temperature and pressure, k(T, p), and reports the least-squares most-likelihood coefficients for the Chebyshev-polynomial expression. (See Chebyshev-polynomial fit section for details.)   The results are written to a CSV file, basename_fitcheb_out.csv.   Optionally, it scans the number of the parameters in order to determine the optimal number of parameters.  

An example input file is shown below.

# Chebyshev-polynomials fit input sample
tempCheb 300 3000
pressCheb 0.01 1000
numPars 7 3
TPk_Table{
  301.671  0.010734434  6.23141E-12
   :
}

The first line is a comment.   The keys, 'tempCheb' and 'pressCheb', are used to specify the range of temperature and pressure, and the key, 'numPars', specifies the numbers of parameters in temperature and pressure axes.   The block enclosed by 'TPk_Table{' and '}' is the data of k(T, p)'s used for the fitting.

tempCheb T_min T_max

  Specifies the range of the temperature (unit: K).

pressCheb P_min P_max

  Specifies the range of the pressure (unit: atm).

numPars nParT nParP

  Specifies the numbers of the parameters in temperature axis (nParT) and pressure axis (nParP).   When either of the numbers is input as zero (0) or negative, the program scans the numbers of the parameters and the output tables of the standard deviation (STD), mean absolute deviation (MAD), and maximum absolute deviation (MAXAD) of log₁₀k into a CSV-format file, basename_fitcheb_diag.csv, which may be useful to determine the optimal numbers of the parameters.

TPk_Table{
  T1 P1 k1
  T2 P2 k2
  :
}

  In the block, a set of temperature, pressure, and rate coefficient should be written in one line in this order (T, p, k).   Any number of data set can be placed in the block.   It should be noted that the number of data sets must be larger than (or equal to) the total number of parameters, that is, nParT × nParP.
  The data sets are preferably prepared on the Gauss-Chebyshev grid, though it is not a strict requirement.

  The results are written to a csv-format file, basename_fitcheb_out.csv.   When either of the numbers of the parameters for temperature and pressure is input as zero or negative, the results of the scan is stored in a csv-format file, basename_fitcheb_diag.csv.