Hi:
Does this work for you?
> yy
Q20 Q21 Q22 Q23 Q24
1 0 1 2 3 4
2 1 NA 2 3 4
3 2 1 2 3 4
rowSums(yy, na.rm = TRUE)
1 2 3
10 10 12
# Use a subset of the variables in yy:
selectVars <- paste('Q', c(20, 21, 24), sep = '')
rowSums(yy[, selectVars], na.rm = TRUE)
1 2 3
5 5 7
HTH,
Dennis
On Sun, Nov 20, 2011 at 12:38 PM, Ian Strang <hamame...@ntlworld.com> wrote:
>
> I am fairly new to R and would like help with the problem below. I am trying
> to sum and count several rows in the data frame yy below. All works well as
> in example 1. When I try to add the columns, with an NA in Q21, I get as NA
> as mySum. I would like NA to be treated as O, or igored.
> I wrote a function to try to count an NA element as 0, Example 3 function.
> It works with a few warnings, Example 4, but still gives NA instead of the
> addition when there is an NA in an element.
>
> In Example 6 & 7, I tried using sum() but it just sums the whole data frame,
> I think,
>
> How do I add together several columns giving the result for each row in
> mySum? NA should be treated as a 0. Please, note, I do not want to sum all
> the columns, as I think rowSums would do, just the selected ones.
>
> Thanks for your help.
> Ian,
>
>> yy <- read.table( header = T, sep=",", text = ## to create a data
>> frame
> + "Q20, Q21, Q22, Q23, Q24
> + 0,1, 2,3,4
> + 1,NA,2,3,4
> + 2,1, 2,3,4")
> + yy
> Q20 Q21 Q22 Q23 Q24
> 1 0 1 2 3 4
> 2 1 NA 2 3 4
> 3 2 1 2 3 4
>
>> x <- transform( yy, ############## Example 1
> + mySum = as.numeric(Q20) + as.numeric(Q22) + as.numeric(Q24),
> + myCount =
> as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24))
> + )
> + x
> Q20 Q21 Q22 Q23 Q24 mySum myCount
> 1 0 1 2 3 4 6 3
> 2 1 NA 2 3 4 7 2
> 3 2 1 2 3 4 8 3
>>
> + x <- transform( yy, ################ Example 2
> + mySum = as.numeric(Q20) + as.numeric(Q21) + as.numeric(Q24),
> + myCount =
> as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24))
> + )
> + x
> Q20 Q21 Q22 Q23 Q24 mySum myCount
> 1 0 1 2 3 4 5 3
> 2 1 NA 2 3 4 NA 2
> 3 2 1 2 3 4 7 3
>
>> NifAvail <- function(x) { if (is.na(x)) x<-0 else x <- x ###############
>> Example 3
> + return(as.numeric(x))
> + } #end function
> + NifAvail(5)
> [1] 5
> + NifAvail(NA)
> [1] 0
>
>> x <- transform( yy,
> + mySum = NifAvail(Q20) + NifAvail(Q22) + NifAvail(Q24),
> ############### Example 4
> + myCount =
> as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24))
> + )
> Warning messages:
> 1: In if (is.na(x)) x <- 0 else x <- x :
> the condition has length > 1 and only the first element will be used
> 2: In if (is.na(x)) x <- 0 else x <- x :
> the condition has length > 1 and only the first element will be used
> 3: In if (is.na(x)) x <- 0 else x <- x :
> the condition has length > 1 and only the first element will be used
>> x
> Q20 Q21 Q22 Q23 Q24 mySum myCount
> 1 0 1 2 3 4 6 3
> 2 1 NA 2 3 4 7 2
> 3 2 1 2 3 4 8 3
>> x <- transform( yy,
> + mySum = NifAvail(Q20) + NifAvail(Q21) + NifAvail(Q24),
> ################ Example 5
> + myCount =
> as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24))
> + )
> Warning messages:
> 1: In if (is.na(x)) x <- 0 else x <- x :
> the condition has length > 1 and only the first element will be used
> 2: In if (is.na(x)) x <- 0 else x <- x :
> the condition has length > 1 and only the first element will be used
> 3: In if (is.na(x)) x <- 0 else x <- x :
> the condition has length > 1 and only the first element will be used
>> x
> Q20 Q21 Q22 Q23 Q24 mySum myCount
> 1 0 1 2 3 4 5 3
> 2 1 NA 2 3 4 NA 2
> 3 2 1 2 3 4 7 3
>
>
>> x <- transform( yy, ############
>> Example 6
> + mySum = sum(as.numeric(Q20), as.numeric(Q21), as.numeric(Q23), na.rm=T),
> + myCount =
> as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24))
> + )
> + x
> Q20 Q21 Q22 Q23 Q24 mySum myCount
> 1 0 1 2 3 4 14 3
> 2 1 NA 2 3 4 14 2
> 3 2 1 2 3 4 14 3
>
>> x <- transform( yy, #############
>> Example 7
> + mySum = sum(as.numeric(Q20), as.numeric(Q22), as.numeric(Q23), na.rm=T),
> + myCount =
> as.numeric(!is.na(Q20))+as.numeric(!is.na(Q21))+as.numeric(!is.na(Q24))
> + )
> + x
> Q20 Q21 Q22 Q23 Q24 mySum myCount
> 1 0 1 2 3 4 18 3
> 2 1 NA 2 3 4 18 2
> 3 2 1 2 3 4 18 3
>
> ______________________________________________
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>
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