Reading two-line headers in R

Question

What is the best way to read a file into R when the header has two necessary lines for the header?

This happens to me all the time, as people often use one line for

Answer 1

Use readLines with 2 for the limit, parse it, paste0 them together, then read in with read.table with skip =2 and header=FALSE (the default). Finish the process off with assignment of the column names:

dat <- "trt biomass yield
 crop   Mg/ha   bu/ac
 C2 17.76   205.92
 C2 17.96   207.86
 CC 17.72   197.22
 CC 18.42   205.20
 CCW    18.15   200.51
 CCW    17.45   190.59
 P  3.09    0.00
 P  3.34    0.00
 S2 5.13    49.68
 S2 5.36    49.72
 "

You would probably use a file argument but using the text argument to the read-functions makes this more self-contained:

 readLines(textConnection(dat),n=2)
#[1] "trt\tbiomass\tyield" "crop\tMg/ha\tbu/ac" 
 head2 <- read.table(text=readLines(textConnection(dat),n=2), sep="\t", stringsAsFactors=FALSE)
 with(head2, paste0(head2[1,],head2[2,]) )
# [1] "trtcrop"      "biomassMg/ha" "yieldbu/ac"  
 joinheadrs <- with(head2, paste0(head2[1,],head2[2,]) )

newdat <- read.table(text=dat, sep="\t",skip=2)
colnames(newdat)<- joinheadrs
#-------------------
> newdat
   trtcrop biomassMg/ha yieldbu/ac
1       C2        17.76     205.92
2       C2        17.96     207.86
3       CC        17.72     197.22
4       CC        18.42     205.20
5      CCW        18.15     200.51
6      CCW        17.45     190.59
7        P         3.09       0.00
8        P         3.34       0.00
9       S2         5.13      49.68
10      S2         5.36      49.72

Might be better to use paste with an underscore-sep:

joinheadrs <- with(head2, paste(head2[1,],head2[2,] ,sep="_")  )
joinheadrs
#[1] "trt_crop"      "biomass_Mg/ha" "yield_bu/ac"