R help - Jul 2009 - How to combine two rows (in a dataframe) into a third row?

Dear R-helpers,

I have two rows in my dataframe:

ID    VALUE
1A    10
1B    15

and I would like to combine these two rows into a single (new) row in my
dataframe:

ID    VALUE
1    25

...simply by specifying a new value for ID and summing the two VALUES.

I have been trying to do this with with rbind, but it's not working.

I'd appreciate any pointers.

Thanks, Mark Na

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Tena koe Mark

?tapply

with the index argument some suitable substring of your ID column.

HTH ....

Peter Alspach 
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Mark Na
> Sent: Friday, 10 July 2009 10:28 a.m.
> To: r-help at r-project.org
> Subject: [R] How to combine two rows (in a dataframe) into a 
> third row?
> 
> Dear R-helpers,
> 
> I have two rows in my dataframe:
> 
> ID    VALUE
> 1A    10
> 1B    15
> 
> and I would like to combine these two rows into a single 
> (new) row in my
> dataframe:
> 
> ID    VALUE
> 1    25
> 
> ...simply by specifying a new value for ID and summing the two VALUES.
> 
> I have been trying to do this with with rbind, but it's not working.
> 
> I'd appreciate any pointers.
> 
> Thanks, Mark Na
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
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Try this:

aggregate(x["VALUE"], list(substr(x[,"ID"], 1, 1)), sum)

On Thu, Jul 9, 2009 at 7:27 PM, Mark Na <mtb954@gmail.com> wrote:
> Dear R-helpers,
>
> I have two rows in my dataframe:
>
> ID    VALUE
> 1A    10
> 1B    15
>
> and I would like to combine these two rows into a single (new) row in my
> dataframe:
>
> ID    VALUE
> 1    25
>
> ...simply by specifying a new value for ID and summing the two VALUES.
>
> I have been trying to do this with with rbind, but it's not working.
>
> I'd appreciate any pointers.
>
> Thanks, Mark Na
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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