R using fread colClasses or skip arguments to read csv with no column headers

Question

I would like to be able to skip a column that is read into R via `data.table`'s `fread` function in v1.8.9. But the csv I am reading in, has no column headers…which appears to be a problem for fread... is there a way to just specify that I don't want specific columns? Would it be better to just pre-allocate a column name and then let it read it in so that it can be skipped? To give an example, I downloaded the data from the following URL http://www.truefx.com/dev/data/2013/MAY-2013/AUDUSD-2013-05.zip unzipped it… and read the csv into R using fread and it has pretty much the same file name just with the csv extension. ``` system.time(pp <- fread("AUDUSD-2013-05.csv",sep=",")) user system elapsed 16.427 0.257 16.682 head(pp) V1 V2 V3 V4 1: AUD/USD 20130501 00:00:04.728 1.03693 1.03721 2: AUD/USD 20130501 00:00:21.540 1.03695 1.03721 3: AUD/USD 20130501 00:00:33.789 1.03694 1.03721 4: AUD/USD 20130501 00:00:37.499 1.03692 1.03724 5: AUD/USD 20130501 00:00:37.524 1.03697 1.03719 6: AUD/U…

Accepted Answer

I think the argument you're looking for is `drop`. Try:

```
require(data.table)  # 1.9.2+
pp <- fread("AUDUSD-2013-05.csv", drop = 1)
```

Note that you can `drop` by name or position.

```
fread("AUDUSD-2013-05.csv", drop = c("columThree","anotherColumnName"))

fread("AUDUSD-2013-05.csv", drop = 10:15)  # read all columns other than 10:15
```

And you can `select` by name or position, too.

```
fread("AUDUSD-2013-05.csv", select = 10:15)  # read only columns 10:15

fread("AUDUSD-2013-05.csv", select = c("columnA","columnName2"))
```

These arguments were added to v1.9.2 (released to CRAN in Feb 2014) and are documented in `?fread`. You'll need to upgrade to use them.

R using fread colClasses or skip arguments to read csv with no column headers

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