Error: Index exceeds matrix dimensions.

So I'm trying to access the column of a matrix called EEG.data that I created: EEG.data(chan,:) and I keep getting: Index exceeds matrix dimensions. However, I am able to access EEG.data(chan) which returns the following:

>>EEG.data(chan)

ans =

126.8809   25.0000

and >>size(EEG.data)

ans =

          48      233268

Maybe I'm misunderstanding the use of :, but what exactly is my issue here?

[the cyclist]

What is the value of chan itself?

Answer 1

[the cyclist]

Just a guess here, but I bet you are doing the equivalent of this:

>> A = magic(7);
>> chan = [3 40];
>> A(chan)

ans =

      46    44

>> A(chan,:)
Index exceeds matrix dimensions.

In the first case (which works), you are actually using a linear index to access the 3rd and then the 40th element (counting down successive columns).

In the second case (which gives an error), the syntax is such that you are trying to access the 3rd and 40th rows of A. Hence, the index exceeds the dimension.

[Dude]

Ahhh I see. I thought that A(chan,:) meant it indexed the same elements as A(chan) did plus the columns they were contained in. Thanks!

[the cyclist]

No problem. As you may have figured out, ":" actually means "all elements along this dimension".