Subtracting 2 cells in an array

Given:

A=[1,3,5,2,6,1];

Is there a function where I can get a difference of first and following cell in above matrix?

For example, output should be = 1-3, 3-5, 5-2,2-6,6-1 = -2,-2,3,-4,5

Finally, is there a way to sum the entire value in the matrix?

Thanks

Answer 1

[Stephen23]

>> -diff(A)
ans =
    -2    -2     3    -4     5
>> sum(-diff(A))
ans =
     0

[Daniel Lee]

thanks. could you please explain why u put negative sign before diff?

[Stephen23]

"could you please explain why u put negative sign before diff?"

Because a-b == -(b-a)

In your question you specified that you wanted "...output should be = 1-3...", which is A(1)-A(2). By definition diff returns A(2)-A(1), but simply negating that gives what you asked for: A(1)-A(2) == -(A(2)-A(1))

Another option would be to use indexing and subtraction (but is likely to be less efficient than diff):

>> A = [1,3,5,2,6,1];
>> A(1:end-1)-A(2:end)
ans =
    -2    -2     3    -4     5
>> -diff(A)
ans =
    -2    -2     3    -4     5

[Daniel Lee]

ahhh. i see. thanks