Replacing rows in R

Question

In R am reading a file with comments as csv using

read.data.raw = read.csv(inputfile, sep='\t', header=F, comment.char='')

The file looks like this:

#comment line 1
data 1<tab>x<tab>y
#comment line 2
data 2<tab>x<tab>y
data 3<tab>x<tab>y

Now I extract the uncommented lines using

comment_ind = grep( '^#.*', read.data.raw[[1]])
read.data = read.data.raw[-comment_ind,]

Which leaves me:

 data 1<tab>x<tab>y
 data 2<tab>x<tab>y
 data 3<tab>x<tab>y

I am modifying this data through some separate script which maintains the number of rows/cols and would like to put it back into the original read data (with the user comments) and return it to the user like this

#comment line 1
modified data 1<tab>x<tab>y
#comment line 2
modified data 2<tab>x<tab>y
modified data 3<tab>x<tab>y

Since the data I extracted in read.data preserves the row names row.names(read.data), I tried

original.read.data[as.numeric(row.names(read.data)),] = read.data

But that didn't work, and I got a bunch of NA/s

Any ideas?

Answer 1

Does this do what you want?

read.data.raw <- structure(list(V1 = structure(c(1L, 3L, 2L, 4L, 5L),
   .Label = c("#comment line 1", "#comment line 2", "data 1", "data 2", 
   "data 3"), class = "factor"), V2 = structure(c(1L, 2L, 1L, 2L, 2L), 
   .Label = c("", "x"), class = "factor"), V3 = structure(c(1L, 2L, 1L,
   2L, 2L), .Label = c("", "y"), class = "factor")), .Names = c("V1", 
   "V2", "V3"), class = "data.frame", row.names = c(NA, -5L))

comment_ind = grep( '^#.*', read.data.raw[[1]])
read.data <- read.data.raw[-comment_ind,]
# modify V1
read.data$V1 <- gsub("data", "DATA", read.data$V1)
# rbind() and then order() comments into original places
new.data <- rbind(read.data.raw[comment_ind,], read.data)
new.data <- new.data[order(as.numeric(rownames(new.data))),]