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From: Ulrik Nash on 17 Mar 2010 11:41
This one might be a little tricky, but I hope someone is able to figure it out!

Suppose I have a horizontal vector, A. For example:

A = [2 3 5 5 1 4]

Suppose also that I have two vertical vectors, START and END. For example:

START = [1 3 4 6]

END = [2 5 5 6]

Now I wish to create a vertical vector, which contains the average of the values in A, from the index value contained in START to the index value contained in END. In this example:

AVERAGES = [(2+3)/2 (5+5+1)/3 (5+1)/2 4/1)]

I appreciate the help.

Regards,

Ulrik.
From: dpb on 17 Mar 2010 12:36
Ulrik Nash wrote:
....

> Suppose I have a horizontal vector, A. For example:
>
> A = [2 3 5 5 1 4]
>
> Suppose also that I have two vertical vectors, START and END. For example:
>
> START = [1 3 4 6]
>
> END = [2 5 5 6]
>
> Now I wish to create a vertical vector, which contains the average of
> the values in A, from the index value contained in START to the index
> value contained in END. In this example:
....

Straightahead sol'n -- use S and E for brevity

avg=zeros(length(S),1); % preallocate
for idx=1:length(S)
avg(idx) = mean(A(S(idx):E(idx)));
end

--
From: Matt J on 17 Mar 2010 15:09

arrayfun(@(s,e) mean(A(s:e)),START,END)
From: dpb on 17 Mar 2010 15:28
Matt J wrote:
>
> arrayfun(@(s,e) mean(A(s:e)),START,END)

Yeah, the "modern" way to implement my earlier "straightahead" sol'n...

Unfortunately, here I see

>> help arrayfun

arrayfun.m not found.

>> % :( Wish a retired geezer could justify the upgrade cost...

I've complai^h^h^h^h^hpled before but TMW doesn't seem to have much
pity... :)

--
From: Matt J on 17 Mar 2010 15:39
dpb <none(a)non.net> wrote in message <hnraj9$oqk$1(a)news.eternal-september.org>...

> Unfortunately, here I see
>
> >> help arrayfun
>
> arrayfun.m not found.
>
> >> % :( Wish a retired geezer could justify the upgrade cost...
>
> I've complai^h^h^h^h^hpled before but TMW doesn't seem to have much
> pity... :)
====================

I wouldn't upgrade for arrayfun alone. It's been observed in various threads that it rarely outperforms a for-loop speed-wise.
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