anonymous function which outputs a vector of sums when the input is a vector of indices.

I'd like to write an anonymous function such as

f = @(X,m,A) sum(X(m:A))

where X is a vector,

m < numel(X),

and A is a subset of

[ m+1,numel(X) ],

which outputs a vector, the i'th element of which is sum(X(m:A(i)))

For example, let

X = [ 1:7 ], m = 4, A = [5:6]

I'd like my function f(X,m,A) to output

[ 4+5, 4+5+6 ]= [ 9 , 15 ]

Thanks for any help!!

[Walter Roberson]

If your A are always going to be consecutive then you can use cumsum()

Answer 1

[per isakson]

Try

>> f = @(X,ix1,ix2) arrayfun( @(ix) sum(X(ix1:ix)), ix2 );
>> f([1:7],4,[5:6])
ans =
     9    15
>> f([1:7],4,[5,7])
ans =
     9    22
>> f([1:7],4,[7,5])
ans =
    22     9

it seems to do it!

[Leo Simon]

Perfect, thanks!