Re: undefined variable in a .m file

[Quentin Spencer]

malik martin wrote:
> hi,
> if i knew the syntax to declare a variable in matlab, then maybe i
> wouldnt be asking this, but i get this error saying:
>
> `a' undefined near line 5 column 11
>
> in this code:
>
> 1   % Read input sound file into vector x(n) and sampling frequency FS
> 2   [x,FS]=wavread('ton2.wav');
> 3   % Sample-by sample algorithm y(n)=a*x(n)
> 4   for n=1:length(x),
> 5   y(n)=a * x(n); <------- ERROR IS HERE
> 6   end;
> 7   % Write y(n) into output sound file with number of
> 8   % bits Nbits and sampling frequency FS
> 9   wavwrite(y,FS,Nbits,'tonealg.wav');
>   

You define a variable by assigning something to it. Try something like

a=2;

before line 5, and it should work. By the way, your for loop in lines 
4-6 is inefficient. You can do the same thing using the command

y = a * x;



Quentin