Drexel dragonThe Math ForumDonate to the Math Forum



Search All of the Math Forum:

Views expressed in these public forums are not endorsed by Drexel University or The Math Forum.


Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: Coding Matlab function "filter" in C++
Replies: 6   Last Post: Feb 11, 2013 11:03 AM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Peter Boettcher

Posts: 3,594
Registered: 12/4/04
Re: Coding Matlab function "filter" in C++
Posted: Nov 30, 2005 12:54 PM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

"Chris Heier" <enygma@gmail.com> writes:

>> y(n) = k2*x(n) + k1*(1+k2)*x(n-1) + x(n-2) - k1*(1+k2)*y(n-1) - k2*y(n-2)
>
> Hey thanks. That answers a ton for me. I guess the last thing I had
> on my mind was in regards to n.
>
> Since X would be a trace containing an array of samples, x[0] would
> contain the first sample. In the algorithm, there is a point where it
> is asking for x[n-1] and x[n-2]. In the case that n would equal 0, the
> first part (n-1) would try to pull a value from the -1 element in the
> array. How would I work around that for the first few elements of the
> array?


Typically the signal is zero-padded. In "help filter", the function
accepts "initial conditions", which would be used instead, in special
applications. Block-based filtering might be one of them, where there
actually are two known values for the input prior to the x[0] in this
context.


--
Peter Boettcher <boettcher@ll.mit.edu>
MIT Lincoln Laboratory
MATLAB FAQ: http://www.mit.edu/~pwb/cssm/



Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© Drexel University 1994-2014. All Rights Reserved.
The Math Forum is a research and educational enterprise of the Drexel University School of Education.