       Re: Manipulating vectors with Position

• To: mathgroup at smc.vnet.net
• Subject: [mg117346] Re: Manipulating vectors with Position
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Wed, 16 Mar 2011 06:24:18 -0500 (EST)

```Array1 = {a, b, c, d, e, f};

Array2 = {{1}, {2, 4, 5}, {3, 6}};

{Total[Array1[[#]]]} & /@ Array2

{{a}, {b + d + e}, {c + f}}

Bob Hanlon

---- Lengyel Tamas <lt648 at hszk.bme.hu> wrote:

==========================
Dear Mathworld Users,
I am tackling a rather straightforward problem. Here it is.

1) I have generated an array of values (Array1)
2) I have generated an array of vectors in Array2, whose Length varies,
and in each subvector the numbers contain the Position (index) of those
elements that I need from Array1. So far so good.

3) What I need is to create a code that picks out those elements from
Array 1 and ads them together if Array2's subvectors have more than 1
element.

Here's an example to make it clear:

Array1 = {a,b,c,d,e,f};  (*a;;f are numbers*)
Array2 = {{1}, {2,4,5}, {3,6}};

My outpout should be: {{a}, {a+d+e}, {c+f}}

I think it is simple, but I can't seem to do it.

Any ideas?

Thank you.

Tam=C3=A1s

```

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