[R] read.table: colClasses when num. of columns is unknown

Vadim Ogranovich vograno at arbitrade.com
Wed Nov 27 22:37:53 CET 2002


I am looking for a way to read tables that have general structure of

characterTag num1 num2 ...

i.e. one character column followed by an unknown to the caller (but fixed
throughout the file) number of numeric columns. I wanted to improve the
speed of read.table by using colClasses, but that seemed to require
knowledge of the actual number of columns in the file. For example I tried
colClasses=c("character", rep("numeric", 100)), here 100 is an upper
boundary on the number of columns, and hoped read.table() would just ignore
the unused entries. But read.table failed and printed an error message
(proving once again that R is a production-strength software).
Is there any way around? Note that my files do have headers so the number of
columns should be known to read.table once it parses the header.


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