R help - May 2013 - Sum objects in a column between an interval defined by conditions on another column

This comes as an application to this question:
http://stackoverflow.com/questions/5896648/sum-object-in-a-column-between-an-interval-defined-by-another-column/5897695#comment23166107_5897695

What I would like to know is how to adjust the answer if I want to sum the
values in B, for ((A[i+1]-A[i]==0) or (A[i+1]-A[i]==1) or (A[i]-A[i-1]==0)
or (A[i]-A[i-1]==1)) where i is the row index, so basically sum B rows for
A-s that have the same value +/- 1, but not sum the same row twice?
I tried building a loop function but I get stuck when using row indices
with data frames. So if I have the next data frame:

 df
       A B
 [1,]  1 4
 [2,]  1 3
 [3,]  3 5
 [4,]  3 7
 [5,]  4 3
 [6,]  5 2



The result I would obtain(considering that when I have ), would be:

 df
       A B
 [1,]  1 7
 [2,]  3 15
 [3,]  5 2


- Nanami

	[[alternative HTML version deleted]]

Hi

Just a question. Why you do not sum 5 with 3 and 4 or leave 3 alone and sum 4
and 5?

Basically combination of cut and aggregate gives you what you want, but tricky
is how to do the cut operation based on your requirements and data

aggregate(df$B, list(df$A), sum)

aggregates B for any single value of A.

However I am not sure how to change A to set of levels based on your
description. For this particular df it can be done by

aggregate(df$B, list(cut(df$A, c(0,1,2,4,6))), sum)

But it is not a general solution.

Petr

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Adriana Pitea
> Sent: Wednesday, May 01, 2013 3:42 PM
> To: r-help at r-project.org
> Subject: [R] Sum objects in a column between an interval defined by
> conditions on another column
> 
> This comes as an application to this question:
> http://stackoverflow.com/questions/5896648/sum-object-in-a-column-
> between-an-interval-defined-by-another-
> column/5897695#comment23166107_5897695
> 
> What I would like to know is how to adjust the answer if I want to sum
> the values in B, for ((A[i+1]-A[i]==0) or (A[i+1]-A[i]==1) or (A[i]-
> A[i-1]==0) or (A[i]-A[i-1]==1)) where i is the row index, so basically
> sum B rows for A-s that have the same value +/- 1, but not sum the same
> row twice?
> I tried building a loop function but I get stuck when using row indices
> with data frames. So if I have the next data frame:
> 
>  df
>        A B
>  [1,]  1 4
>  [2,]  1 3
>  [3,]  3 5
>  [4,]  3 7
>  [5,]  4 3
>  [6,]  5 2
> 
> 
> 
> The result I would obtain(considering that when I have ), would be:
> 
>  df
>        A B
>  [1,]  1 7
>  [2,]  3 15
>  [3,]  5 2
> 
> 
> - Nanami
> 
> 	[[alternative HTML version deleted]]
> 
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