Re: [R] Conditionally constructing columns in a data frame

From: Erik Iverson <eriki_at_ccbr.umn.edu>
Date: Tue, 29 Jun 2010 13:59:08 -0500

I'm sure there's an easier way, but it's going to be easiest to get a useful response if we have a reproducible, minimal example, as the posting guide requests. ?tapply is probably involved.

Stuart Luppescu wrote:
> Hello, I have to construct 5 new columns in a data frame depending on
> the value of another of the columns in the data frame. The only way I
> could figure out to do this was to subset the data frame five times, do
> the variable construction, and then rbind the subsets back together.
> Here's part of the code I used:
>
> read001 <- read[read$existstr=="001",]
>
> read001$era1end <- NA
> read001$era2base <- NA
> read001$era2end <- NA
> read001$era3base <- read001$era1base
> read001$era3end <- read001$era3base + (6 * read001$era3tr)
>
> read011 <- read[read$existstr=="011",]
>
> read011$era1end <- NA
> read011$era2base <- read011$era1base
> read011$era2end <- read011$era2base + (4 * read011$era2tr)
> read011$era3base <- read011$era2end
> read011$era3end <- read011$era2end + (6 * read011$era3tr)
>
> ...
>
> read2 <- rbind(read001, read011, read100, read110, read111)
>
>
> Isn't there an easier way to do this?
>
> Thanks.
>



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