Thread Subject:

erron in code

Can someone tell me what is the error in this?
y=randn(500,1);
N=length(y);
f=1;
for t=10:30
n=f*t;
kapa=N/n;
kapa=round(kapa);
i=0;
clear alpha
clear alphadetrend
clear Y
while (i+n)<N
    for j=1:kapa
    alpha(1:n,j)=y(i+1:i+n,1);
    alphadetrend(1:n,j)=detrend(alpha(1:n,j));
    i=i+n;
    end
end
i=1;
while i<=N
    for j=1:kapa
        for k=1:n
            Y(i,1)=alphadetrend(k,j);
            i=i+1;
        end
    end
end
end

The first loop runs OK. But then when t becomes 11 it says that in line alpha(1:n,j)=y(i+1:i+n,1); index exceeds matrix dimensions. I tried to put an if to check the index i+1 too but it still gives the same error. Any ideas what is wrong?
Thanks in advance!

On 10/12/2012 10:18 AM, Konst wrote:
> Can someone tell me what is the error in this?
> y=randn(500,1);
> N=length(y);
> f=1;
> for t=10:30
> n=f*t;
> kapa=N/n;
> kapa=round(kapa);
> i=0;
> clear alpha
> clear alphadetrend
> clear Y
> while (i+n)<N
> for j=1:kapa
> alpha(1:n,j)=y(i+1:i+n,1);
> alphadetrend(1:n,j)=detrend(alpha(1:n,j));
> i=i+n;
> end
> end
...

>
> The first loop runs OK. But then when t becomes 11 it says that in line
> alpha(1:n,j)=y(i+1:i+n,1); index exceeds matrix dimensions. I tried to
> put an if to check the index i+1 too but it still gives the same error.
> Any ideas what is wrong? Thanks in advance!

t
t =
     11
 >> j
j =
      5
 >> size(alpha)
ans =
     11 4
...

--

"Konst " <konstance1@hotmail.com> wrote in message <k59cbj$2le$1@newscl01ah.mathworks.com>...
> The first loop runs OK. But then when t becomes 11 it says that in line alpha(1:n,j)=y(i+1:i+n,1); index exceeds matrix dimensions. .....
- - - - - - - - - -
  I don't see any error at t = 11, but at t = 12 you will have kapa = 42 and, because 12*42 = 504, at the last trip through the for-lop you will call on y(493:504) which is out of range. You had better change from round(kapa) to floor(kapa).

Roger Stafford

"Roger Stafford" wrote in message <k59u2b$e4c$1@newscl01ah.mathworks.com>...
> "Konst " <konstance1@hotmail.com> wrote in message <k59cbj$2le$1@newscl01ah.mathworks.com>...
> > The first loop runs OK. But then when t becomes 11 it says that in line alpha(1:n,j)=y(i+1:i+n,1); index exceeds matrix dimensions. .....
> - - - - - - - - - -
> I don't see any error at t = 11, but at t = 12 you will have kapa = 42 and, because 12*42 = 504, at the last trip through the for-lop you will call on y(493:504) which is out of range. You had better change from round(kapa) to floor(kapa).
>
> Roger Stafford

But isn't the while supposed to control that I am below 500?
I changed to floor but it still gives me the same mistake at t=11. Then I did this:

    for j=1:kapa
      if (i+n)<N
      alpha(1:n,j)=y(i+1:i+n,1);
      alphadetrend(1:n,j)=detrend(alpha(1:n,j));
      i=i+n;
      end
    end
i=1;
    for j=1:kapa
        for k=1:n
            if i<=N
            Y(i,1)=alphadetrend(k,j);
            i=i+1;
            end
        end
    end
which I think does exactly the same but I was aimin to have better control over the indexes. Still the same error though.

"Konst " <konstance1@hotmail.com> wrote in message <k5bve6$fte$1@newscl01ah.mathworks.com>...
> I changed to floor but it still gives me the same mistake at t=11. .....
 - - - - - - - -
  My advice to you would be to insert an appropriate 'fprintf' line immediately prior to your error-producing line to see what is going on at the time of the error, perhaps something like this:

    ...
    for j=1:kapa
    fprintf('i = %d, n = %d, size(y,1) = %d\n',i,n,size(y,1)) % <--
    alpha(1:n,j)=y(i+1:i+n,1);
    ...

You will get a lot of print-out lines but it will be the last one before the error that you will be interested in. It may lead you to the source of the trouble.

Roger Stafford