[R] Summing using a boolean index vector (repost in plain text).

[Dan Stanger]

Hello Jim,
Thank you for getting back to me.  Cumsum does exactly what I needed as the following example shows.

[1]  TRUE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE  TRUE FALSE
> cumsum(x)
 [1]  1  1  1  1  2  2  2  2  2  3  3  3  3  3  4  4  4  4  4  5  5  5  5  5  6  6  6  6  6  7  7  7  7

Dan Stanger
Eaton Vance Management
200 State Street
Boston, MA 02109
617 598 8261


-----Original Message-----
From: jim holtman [mailto:jholtman at gmail.com] 
Sent: Friday, June 18, 2010 12:24 PM
To: Dan Stanger
Cc: R-help at r-project.org
Subject: Re: [R] Summing using a boolean index vector (repost in plain text).

?cumsum
?ave

 But without data (follow the posting guide) specific solution can not
be specified

On Fri, Jun 18, 2010 at 11:39 AM, Dan Stanger <DStanger at eatonvance.com> wrote:
> Hello all:
> I have a dataframe f of weekdays and value, and a Boolean vector with Fridays set to true, and other days set to false, created by fridays<-(diff(f$weekdays) < -1).
> I would like to create a vector of sums, for each week.  That is, start summing on the first false value in the vector, and when I get to true, produce the sum, and start summing again.
> Is there a vector operation which can do this, without writing an explicit loop?
> Thank you,
> Dan Stanger
> P.S. Sorry about the repost.
> Eaton Vance Management
> 200 State Street
> Boston, MA 02109
> 617 598 8261
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?