Replace NA values by row means

I want to replace my NA values from a matrix acquired by :

read.table(…)

Those values should be the mean of the corresponding row.

I.e, the following row of the table :

1 2 1 NA 2 1 1 2

would become

1 2 1 1.43 2 1 2

Thank you.

Here's some sample data.

m <- matrix(1:16, nrow=4)
m[c(1,4,6,11,16)] <- NA

And here's how I'd fill in missings with the row means.

k <- which(is.na(m), arr.ind=TRUE)
m[k] <- rowMeans(m, na.rm=TRUE)[k[,1]]

Your data will be in a data.frame; you'll have to convert to a matrix first using as.matrix. You may or may not want to leave it in that format; to convert back use as.data.frame.

x[is.na(x)] <- mean(x, na.rm=TRUE)  # for vectors or for a matrix as a whole

t( apply(x, 1, function(xv) { xv[is.na(xv)] <- 
                                    mean(xv, na.rm=TRUE)
                              return(xv)}
          ) ) # for a row-oriented sol'n

a = c(NA, 1, 2, 3, 10)
a[which(is.na(a)==TRUE)] = mean(a,na.rm = T)