On Nov 20, 2011, at 3:38 PM, Ian Strang 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.
"Ignored" is by far the better option and that is easily accomplished
by reading the help page for 'sum' and using the obvious parameter
settings.
?sum
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,
It sums whatever you give it.
How do I add together several columns giving the result for each row
in mySum?
?rowSums # which also has the same parameter setting for dealing with
NAs.
NA should be treated as a 0.
Nooo , noooo, nooooooooo. If it's missing it's not 0.
Please, note, I do not want to sum all the columns, as I think
rowSums would do, just the selected ones.
Fine. then select them:
?["
--
David.
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
______________________________________________
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.
David Winsemius, MD
West Hartford, CT
______________________________________________
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.
