[R] a strange behavior with ifelse
jim holtman
jholtman at gmail.com
Sat Apr 9 04:07:38 CEST 2011
try this:
> a=c(2,NA,NA,NA,2,2,NA,2,NA,2)
> b=c(NA,1,1,NA,2,2,2,2,2,2)
> c1 <- ifelse((!is.na(a) & a == 1) | (!is.na(b) & b == 1)
+ , 1
+ , ifelse((!is.na(a) & a == 2) | (!is.na(b) & b == 2)
+ , 2
+ , NA
+ )
+ )
> cbind(a, b, c1)
a b c1
[1,] 2 NA 2
[2,] NA 1 1
[3,] NA 1 1
[4,] NA NA NA
[5,] 2 2 2
[6,] 2 2 2
[7,] NA 2 2
[8,] 2 2 2
[9,] NA 2 2
[10,] 2 2 2
>
On Fri, Apr 8, 2011 at 1:56 PM, wgu <wgu at uab.edu> wrote:
> I have used R for years but run into a seemingly simple problem involving 'ifelse'. condensed code like this
>
> a=c(2,NA,NA,NA,2,2,NA,2,NA,2)
> b=c(NA,1,1,NA,2,2,2,2,2,2)
>
> #I want to combined a and b into c so that c would be a valid number either a or b is not missing
>
> c=ifelse(a==1|b==1,1,ifelse(a==2|b==2,2,NA))
> cbind(a,b,c)
>
> a b c
> [1,] 2 NA NA
> [2,] NA 1 1
> [3,] NA 1 1
> [4,] NA NA NA
> [5,] 2 2 2
> [6,] 2 2 2
> [7,] NA 2 NA
> [8,] 2 2 2
> [9,] NA 2 NA
> [10,] 2 2 2
>
> look at rows 1, 7 and 9, c supposes to be 2 but got NA instead. seemingly, the second 'ifelse' doesn't perform as it supposes.
>
> my R version is 2.12.2
>
> any suggestion
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>
--
Jim Holtman
Data Munger Guru
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