Re: Syntax befuddlement

[Henry F. Mollet]

Thanks for earlier expose on octave for Mac/Fink/DarvinPort.

I've checked below statement with a simple-minded test using a real x and t
and it worked but it may not be a meaningful test:
octave:1> x=rand (1,10)
x =
 Columns 1 through 7:
  0.925892  0.410042  0.170498  0.240161  0.811388  0.024802  0.997211
 Columns 8 through 10:
  0.773300  0.687108  0.668670
octave:2> t = [2:9]
t =
  2  3  4  5  6  7  8  9
octave:4> fnormhat=0.5*(angle(-x(t+1).*conj(x(t-1)))+pi)/(2*pi)
fnormhat =
  0.50000  0.50000  0.50000  0.50000  0.50000  0.50000  0.50000  0.50000
Henry

on 12/26/03 8:14 PM, Joe Koski at address@hidden wrote:

> I'm trying to use a MatLab routine that I found on the net for calculating
> instantaneous local frequency after a Hilbert transform. The hilbert.m
> routine (called from octave-forge) completes successfully. The amplitude of
> the signal is correctly calculated from the results. In attempting to
> calculate frequency and convert the remainder of the MatLab routine to
> octave, I get errors during execution terminating with:
> 
> error: invalid vector index = -1
> 
> The statement that is being evaluated at the time of the error is
> 
> fnormhat=0.5*(angle(-x(t+1).*conj(x(t-1)))+pi)/(2*pi);
> 
> where x is a real column vector (representing data) of length 256, and t is
> a real row vector (representing time "instants," but with the first and last
> values truncated) of length 254.
> 
> When I try this with the --braindead option, the routine gives no errors,
> but then no results are returned, either. The date on this script is 1994
> and it's currently posted on the web, so it probably really does work in
> MatLab.
> 
> As an old Fortran programmer, the statement syntax seems very strange to me.
> 
> My questions: 
> 
> How can one real array with increments (t+1, t-1) be an index for another
> real array (x)? Or does that indicate a functional relationship?
> 
> Is this standard octave?
> 
> Are there tricks for getting MatLab scripts like this to execute correctly
> in octave?
> 
> Alternatively, are there an equivalent octave-forge routines that would
> avoid the problem?
> 
> If it would help, I could include more of the routine.
> 
> Thanks.
> 
> Joe Koski
> 
> 
> 
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