implementing filters

[E. Joshua Rigler]

I'm a little confused on how to translate a typical filter equation
making use of a "delay", or "forward shift" operator (the "q" in the
following equation) into a standard difference equation.  As a result,
I'm not sure if I'm using filter.oct correctly.  If I have an equation
like:

             1
  yf(k) =  ---- y(k)
           F(q)


where y is my input, F(q) is some causal filter, and yf is my output,
shouldn't this be the same as:


  yf(k) = -1 * ( f(1)*y(k-1) + f(2)*y(k-2) +...+ f(n)*y(k-n))


which I could then implement in Octave with:


  yf = filter ( [0,-1*F], 1, y);


Thanks in advance for any advice.

-EJR



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