%function [freq,mag] = terpol(freqin,magin,npts)
%   this function interpolates the irregularly spaced
%   frequency/magnitude data FREQIN and MAGIN,
%   in the following way. first, it assumes that
%   FREQIN is a row vector of nonnegative frequencies,
%   between 0 and pi:
%   foreach 1 <= i <= NPTS
%      if      pi*(i-1)/NPTS  <  FREQIN(1),
%        then    FREQ(i)  :=  MAG(1)
%      if      FREQIN(length(FREQIN))  <=  pi*(i-1)/NPTS
%        then    MAGOUT((i) =  MAGIN(length(MAGIN)) 
%      for other values of FREQIN(i), the program does
%      linear interpolation between data points               
%

function [freq,mag] = terpol(freqin,magin,npts)
 lmagin = (1/log(10))*log(magin);  
 freq = (pi/npts)*(0:npts-1);
 lmag = zeros(1,npts);
 topval = length(freqin);
 p = find(freq<freqin(1));
 lmag(p) = lmagin(1)*ones(1,length(p));
 p = find(freqin(topval)<=freq);
 lmag(p) = lmagin(topval)*ones(1,length(p));
 for i=2:topval
   p=find(freq>=freqin(i-1) & freq<freqin(i));
   rat = freq(p) - freqin(i-1)*ones(1,length(p));
   rat = (1/(freqin(i)-freqin(i-1)))*rat;
   lmag(p)=(ones(1,length(p))-rat)*lmagin(i-1)+rat*lmagin(i);
 end
 mag = exp(log(10)*lmag);
%
% Copyright MUSYN INC 1991,  All Rights Reserved
