labview equivalent to matlab filter function

[Tudor]

Hi

I have a script In Matlab that is using the built-in filter function in matlab.

y = filter(B,A,x);

were x is the signal to be filtered and A/B is the filter coefficients.

Is there a labview function that gives my the same y as Matlab does if x, A and B is the same.

Best wishes 

[Giedrius.S]

Try Signal Processing -> Filters palette. Also you could try using MatScript node (MathScript module required) for the Matlab commands implemented in LabVIEW directly.

[Tudor]

I have tried the IIR Filter and used A as reverse coefficient and B as forward cofficients with no luck.

[Dennis_Knutson]

'No luck' is a pretty poor description of a problem. Provide some details. Attach your VI with data and explain exactly what you expect and how it is different than what you are seeing.

[Tudor]

🙂 sorry. I post some Matlab code and VI to demonstrate.

Matlab code:

clear;

x = 1:12;

A = [1 2 1 1];

B = [1 1 2 1];

y = filter(B,A,x)

%y =

%

%     1     1     4     2     8     0    17   -10    40   -45   107  -157

%

y2 = filter(B,A,x, [0 1 0]')

%y2 =

%

%     1     2     2     5     3     9     1    18    -9    41   -44   108

% 

 and my VI is attached (screenshot). My Y is correct to the first filter call to matlab (y = y in both lw and matlab). And that is good. But the other call use a the vector Zi = [0 1 0] and from Matlabs help

[Y,Zf] = FILTER(B,A,X,Zi) gives access to initial and final

    conditions, Zi and Zf, of the delays.  Zi is a vector of length

    MAX(LENGTH(A),LENGTH(B))-1, or an array with the leading dimension 

    of size MAX(LENGTH(A),LENGTH(B))-1 and with remaining dimensions 

    matching those of X.

Any idees how this can be done in LabView or what the Zi does in the Matlab implementation?

Message Edited by Tudor on 02-11-2010 09:29 AM

[Tudor]

I tried to run the matlab function filtfilt from LabView but it gives me some edge effects. Doesnt lw MathScript Node use matlab to compute? See my attached screenshot of my vi, matlab .m script and the result plots. Im using the same data and the same script in both matlab and labview.

[GrantM]

Let's follow the MathScript filtfilt discussion in this thread.