Re: how to express sinc * exp?

[Al Goldstein]

I hadn't seen the Matlab Primer lately so I wondered. Didn't see any links
in Mathworks but got it from altavista. The address ftp.math.ufl.edu/pub/matlab

On Thu, 9 Mar 2000, Dirk Laurie wrote:

> eric skryf:
> > 
> > Dear octave expert:
> > 
> >   In matlab toolbox siganl processing:
> > b=0.4*sinc(0.4*(-25:25));
> > [H,w]=freqz(b,1,512,2);
> > plot(w,abs(H));
> > 
> > work
> >  
> > but if I want to let b be the product of sinc and
> > 2*exp(-i*pi)+exp(-i*3*pi)
> > b=0.4*sinc*(2*exp(-i*pi)+exp(-i*3*pi))(0.4*(-25:25));
> > 
> > is not work,
> > I got
> > x undefined near line 24 column 37
> > ..................
> > etc.
> > 
> > how to modify it to work?
> > 
> Dear Eric:
> 
> I and others have seen and sometimes answered quite a few of
> your questions on this list, but sooner or later someone will
> have to say it.  And I'm saying it now:
> 
>    RTFM   (Read The Friendly Manual)
> 
> Get hold of a Matlab primer on the Internet. 
> Several are available by following links from
>    http://www.mathworks.com 
> Or buy yourself one of the many books for teaching yourself
> Matlab.   Most of what they say is applicable to Octave too.
> It will be faster than asking questions on octave-help.
> 
> In the present case,
> 
> b=0.4*sinc*(2*exp(-i*pi)+exp(-i*3*pi))(0.4*(-25:25));
> 
> you have made two mistakes:
> 
> (a)  sinc is a function which requires one argument.
>      You can therefore write "sinc(0.4*(-25:25))"
>      or "x=(0.4*(-25:25)); sinc(x)"
>      but not just sinc.
> 
> (b)  ")(" is never legal syntax.  There must always
>      be an operator.
> 
> The way to code what I think you mean, is:
>    x=(0.4*(-25:25));
>    b=0.4*sinc(x).*(2*exp(-i*pi*x)+exp(-i*3*pi*x))
> 
> Note ".*" for multiplying vectors term by term.
> 
> Dirk Laurie 
> 
> 
> 
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