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## Re: firls.m, part 2

**From**: |
je suis |

**Subject**: |
Re: firls.m, part 2 |

**Date**: |
Fri, 9 Jun 2017 19:24:19 +0000 |

I have discovered the source of the errors: expint(). For purely
imaginary arguments, as their value increases, the results come more
and more worse. I have made a separate version, E1(x), which uses code
adapted from Numerical recipes and, not least, when run with this
line:
x=(1:0.1:100)*1i; tic; a=E1(x); toc, tic; b=expint(x); toc
the timings are almost the same: 0.76s (E1) and 0.72 (expint). This
for eps=1e-15.
I gave uploaded E1.m in the same location on github and, after some
more testing with the 3 examples I have with 1/f^2 weighting [mostly
plotting diff(abs(fft(h)))) ], I dare conclude that my numbers are
better than Matlab's.
Please check the two scripts for whatever input you can think of. When
using 1/f^2 weighting, don't forget that there will be similar
numbers, with larger differences towards the ends of the impulse, and
with a dew common decimals towards the middle, but I dare you to plot
the derivative of the FFT for both: you can clearly see the
exponential rise in the ripple and the (almost) zero ripple close to
DC, in my results. I'm sorry, I can only stay modest for so long. :-)
Vlad

**firls.m, part 2**, *je suis*, `2017/06/07`
**Re: firls.m, part 2**,
*je suis* **<=**
**Re: firls.m, part 2**, *je suis*, `2017/06/18`
**Re: firls.m, part 2**, *Nicholas Jankowski*, `2017/06/19`
**Re: firls.m, part 2**, *Mike Miller*, `2017/06/19`
**Re: firls.m, part 2**, *je suis*, `2017/06/19`
**Re: firls.m, part 2**, *Mike Miller*, `2017/06/19`
**Re: firls.m, part 2**, *je suis*, `2017/06/19`
**Re: firls.m, part 2**, *Dmitri A. Sergatskov*, `2017/06/19`
**Re: firls.m, part 2**, *je suis*, `2017/06/19`
**Re: firls.m, part 2**, *Sergei Steshenko*, `2017/06/21`
**Re: firls.m, part 2**, *Mike Miller*, `2017/06/19`