function remap = remapf2(toindex,factor,fftarr)
% This does interpolation the other way from remapf.
% idea is to use 1/factor to compute the "come from"
% index in the orig. fftarr, for indices 2 - N/2+1
%  then   in the new transposed fftarr.
% fftarr is a row in a breakup array

  len = size(fftarr,2);
    fromindex = (1/factor)*(toindex-1); %count past peak
    newi = floor(fromindex);

    if newi == 0 % freqs being mapped down to lowest
        y0 = complex(0,0);
        y1 = fftarr(2); % interp. btwn 0 and old lowest
        remap = expinterp(fromindex,0,1,y0,y1);
        return;
    elseif  fromindex > (len/2 +1) %damned indexing
        remap= complex(0,0);
        return
    else
        remap = expinterp(fromindex, newi, newi+1, ...
            fftarr(newi+1),fftarr(newi+2));
    end
end


        


