跳过R read.table（）中的列

Question

I wanna skip the first three columns. Couldn't quite understand the posts about colClasses because I'm new to R.

YDL025C YDL025C 1   -0.1725 -0.5375 -0.4970 -0.3818 -0.5270 -0.4260 -0.6929 -0.4020 -0.3263 -0.3373 -0.3532 -0.2771 -0.2732 -0.3307 -0.4660 -0.4314 -0.3135
YKL032C YKL032C 1   -0.2364 0.0794  0.1678  0.2389  0.3847  0.2625  0.1889  0.2681  0.0363  -0.1992 -0.0521 -0.0307 0.0584  0.2817  0.2239  -0.0253 0.0751

Answer 1

If you have to use read.table and you want to filter on the way in, you can use col.classes as follows. You have 20 columns. Say the first 2 are character, rest are numeric and you want to drop 4,5,6. You construct a vector of length 20 detailing that information. The NULL will not pull in those columns.

x<- read.table(file="datat.txt", 
               colClasses = c(rep("character", 2),
                              rep("numeric", 1),
                              rep("NULL", 3),
                              rep("numeric", 14)),
               header = FALSE)
x

       V1      V2 V3      V7      V8      V9     V10     V11     V12     V13     V14     V15     V16     V17     V18     V19     V20
1 YDL025C YDL025C  1 -0.3818 -0.5270 -0.4260 -0.6929 -0.4020 -0.3263 -0.3373 -0.3532 -0.2771 -0.2732 -0.3307 -0.4660 -0.4314 -0.3135
2 YKL032C YKL032C  1  0.2389  0.3847  0.2625  0.1889  0.2681  0.0363 -0.1992 -0.0521 -0.0307  0.0584  0.2817  0.2239 -0.0253  0.0751

Answer 2

As commented above, easier to remove the columns after reading in. For example:

mydf <- read.table("mydf.txt")

Then,

mydf[, 4:ncol(mydf)]

will remove the first 3 columns.