[R] replace NA's with row means for specific columns

[David L Carlson]

This should be a bit quicker since it just loops through the column blocks:

> Zdf <- structure(list(ID = structure(1:4, .Label = c("b", "c", "d", 
+ "e"), class = "factor"), A1 = c(4L, 4L, NA, 4L), A2 = c(5L, 5L, 
+ 5L, 5L), A3 = c(NA, 1L, 1L, 4L), B1 = c(2L, NA, 1L, 5L), B2 = c(NA, 
+ 3L, NA, NA), B3 = c(4L, 4L, 4L, 4L), C1 = c(5L, 5L, 5L, 5L), 
+     C2 = c(1L, 1L, 1L, 1L), C3 = c(3L, 3L, 3L, 3L), C4 = c(NA, 
+     2L, 2L, 2L)), .Names = c("ID", "A1", "A2", "A3", "B1", "B2", 
+ "B3", "C1", "C2", "C3", "C4"), class = "data.frame", row.names = c(NA, 
+ -4L))
> 
> Zdf
  ID A1 A2 A3 B1 B2 B3 C1 C2 C3 C4
1  b  4  5 NA  2 NA  4  5  1  3 NA
2  c  4  5  1 NA  3  4  5  1  3  2
3  d NA  5  1  1 NA  4  5  1  3  2
4  e  4  5  4  5 NA  4  5  1  3  2
> 
> A <- grep("^A", colnames(Zdf))
> B <- grep("^B", colnames(Zdf))
> C <- grep("^C", colnames(Zdf))
> 
> for (i in list(A, B, C)) {
+      mn <- rowMeans(Zdf[, i], na.rm=TRUE)
+      miss <- which(is.na(Zdf[, i]), arr.ind=TRUE)
+      Zdf[, i][miss]<- mn[miss[, 1]]
+ }
> 
> Zdf
  ID A1 A2  A3  B1  B2 B3 C1 C2 C3 C4
1  b  4  5 4.5 2.0 3.0  4  5  1  3  3
2  c  4  5 1.0 3.5 3.0  4  5  1  3  2
3  d  3  5 1.0 1.0 2.5  4  5  1  3  2
4  e  4  5 4.0 5.0 4.5  4  5  1  3  2

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352



-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jim Lemon
Sent: Monday, November 2, 2015 5:33 PM
To: Zahra
Cc: r-help mailing list
Subject: Re: [R] replace NA's with row means for specific columns

Hi again,
Small typo in line 5 - should be

replace_NAs<-function(x,group_lab=c("A","B","C")) {
 for(lab in group_lab) {
  indices<-grep(lab,names(x),fixed=TRUE)
  na_indices<-is.na(x[indices])
  if(any(na_indices))
   x[indices][na_indices]<-rowMeans(x[indices],na.rm=TRUE)
 }
 return(x)
}

Jim

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