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## Re: Using sftrans as matlab's lp2lp

**From**: |
Mike Miller |

**Subject**: |
Re: Using sftrans as matlab's lp2lp |

**Date**: |
Wed, 11 Nov 2015 10:17:40 -0800 |

**User-agent**: |
Mutt/1.5.24 (2015-08-30) |

On Tue, Nov 10, 2015 at 19:32:25 -0800, texidor wrote:
>* Hi,*
>* I have been porting some code but I can not have equal results to moving*
>* lowpass' filter cuting frequency using the sftrans and lp2lp.*
>* *
>* numNorm =*
>* 0 0 0 1.0000*
>* denNorm =*
>* 1.0000 2.0000 2.0000 1.0000*
>* fc=180*
>* *
>* Matlab code uses:*
>* [num,den]=lp2lp(numNorm,denNorm,2*pi*fc);*
>* and returns:*
>* num =*
>* 1.4466e+09*
>* den =*
>* 1.0e+09 **
>* 0.0000 0.0000 0.0026 1.4466*
>* *
>* The octaves function have been seted:*
>* [num,den,sg]=sftrans(numNorm,denNorm,1,2*pi*fc,0);*
>* *
>* returns:*
>* num = 1131.0*
>* den =*
>* 1131.0 2261.9 2261.9 1131.0*
>* *
>* sg = 1.4466e+009*
>* *
>* *
>* Thanks in advance.*
Hi, did you see that the arguments to the sftrans function are the
zero-pole-gain form of the filter? The following gives the same answer
that you reported getting with Matlab:
[z, p, k] = tf2zp (numNorm, denNorm);
[z, p, k] = sftrans (z, p, k, 2*pi*fc, false);
[num, den] = zp2tf (z, p, k);
Cheers,
--
mike

**Using sftrans as matlab's lp2lp**, *texidor*, `2015/11/11`
**Re: Using sftrans as matlab's lp2lp**,
*Mike Miller* **<=**
**Re: Using sftrans as matlab's lp2lp**, *texidor*, `2015/11/12`
**Re: Using sftrans as matlab's lp2lp**, *Mike Miller*, `2015/11/12`
**Re: Using sftrans as matlab's lp2lp**, *Nicholas Jankowski*, `2015/11/12`
**Re: Using sftrans as matlab's lp2lp**, *texidor*, `2015/11/12`
**Re: Using sftrans as matlab's lp2lp**, *Nicholas Jankowski*, `2015/11/12`
**Re: Using sftrans as matlab's lp2lp**, *texidor*, `2015/11/13`