spdiags

[calledol]

Hi,

I'm trying to create a 40000x40000 sparse matrix with 2 diagonals. This is my code:


n = 200;
s = n*n;

for j=1:2
for i=1s-1)
if mod(i,n) == 0
u(i,j) = 0;
else
u(i,j) = 1;
end
end
end

c = [-1;1];

Y = spdiags(u,c,s,s);

When I try to run it i get the following message:

??? Index exceeds matrix dimensions.

Error in ==> spdiags at 114
a((len(k)+1):len(k+1), = [i i+d(k) B(i+(m>=n)*d(k),k)];

Error in ==> uppg3 at 26
Y = spdiags(u,c,s,s);



I don't see where the problem is. Would really appreciate some help.

Best regards
Calle

 

[flash3780]

Looks like an unexpected input to the spdiags function. I'd check and make sure that I were plugging in what I thought I was plugging in.

Here's the reference page from Mathworks:

http://www.mathworks.com/help/techdoc/ref/spdiags.html