[R] Getting tripped up on NAs in trying to create new variable

[Peter Alspach]

Tena koe Greg

df$c <- 0
df[apply(df[,-3], 1, function(x) any(x %in% 3)), 3] <- 1
df[apply(df[,-3], 1, function(x) all(is.na(x))), 3] <- NA
df
   a  b  c
1 NA NA NA
2  2 NA  0
3  2  3  1
4  3 NA  1
5  2  1  0
6 NA  3  1

HTH ....

Peter Alspach

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Greg Blevins
> Sent: Monday, 18 October 2010 2:04 p.m.
> To: r-help at r-project.org
> Subject: [R] Getting tripped up on NAs in trying to create new variable
> 
> Hello R help:
> 
> I have the following data:
> 
> a <- c(NA, 2, 2, 3, 2, NA)
> b <- c(NA, NA, 3, NA, 1, 3)
> df <- data.frame(a, b)
> > df
>    a  b
> 1 NA NA
> 2  2 NA
> 3  2  3
> 4  3 NA
> 5  2  1
> 6  NA 3
> 
> I want to create variable c such that if there is a 3 in either
> variable a
> or variable b, variable c is 1(rows 3, 4 & 6 below).
> 
> If 3 not in a or b and a value appears in a or b, then c is 0(row 2
> below).
> If NA is present in both variables, c is NA (row 1 below).
> 
>    a  b   c
> 1 NA NA   NA
> 2  2 NA   0
> 3  2  3   1
> 4  3 NA   1
> 5  2  1   0
> 6  NA 3   1
> 
> 
> I have tried various ifelse attempts but have not hit upon the correct
> solution yet. For example,
> the following syntax throws NA for row two instead of the hope for "0".
> 
> test <- ifelse(is.na(df$a) & is.na(df$b), NA,
>   ifelse((!is.na(df$a) | !is.na(df$b)) & ((df$a ==3 | df$b == 3)), 1,
> 0))
> > test
> NA NA  1  1  0  1
> 
> Any help much appreciated.
> --
> Gregory L. Blevins
> Office 952 944-5743
> Cell 612 251 0232
> gregblev at gmail.com
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
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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.

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