Indexing problem based on value?

Hi,

I encountered a strange problem. For A= [5 4 3 2 1 0 1 2 3 4 5];

I can't do B = A(1): A(6). The return is 1×0 empty double row vector. if I do A(7): A(8) or start from index 7, I can get the output.

I am not sure what is the source of problem. I expected A(1) : A(6) = [5 4 3 2 1 0].

I tried A(1:6) and it works. what is the difference between A(1:6) and A(1): A(6) while the latter doesn't work?

Thanks.

Answer 1

[KSSV]

B = A(1:6)

You should read about array indexing in MATLAB. MATLAB indices are always nonzero positive integers.

When you use A(1:6), it means in the array A pick indices from 1 to 6.

When you try A(1):A(6), it will try to generate an array with a difference of 1, from the value A(1) i.e 5 to A(6) i.e 0, this will work when start value is low and end value is high, in your case they are 5 and 0, so :, cannot generate an array. Where as try A(6):A(1), it will work.

Answer 2

[SHIVANI CHORGE]

A(1) : A(6)=A(1:6)

A= [5 4 3 2 1 0 1 2 3 4 5]

this is in vector form hence A(1) : A(6) this is not working

if you expected like this A(1) : A(6) = [5 4 3 2 1 0]

than use it

A(1) : A(6)=A(1:6)