Write table row names problems in R

Question

I'm using the write.table() method to write a matrix into a text file. My matrix has row and column names. I noticed that R messes up that names.

First of all names that start with a digit are wrote using X as prefix. For example 1005_at will become X1005_at.

Second characters as - and / are substituted with a dot ..

Why is this happening? Is there a way to avoid this crazy issue?

Answer 1

make.names is used to convert names to syntactically valid ones. Check out this small example:

> make.names(c(".1 - / q", "if", "0", "NA"))
[1] "X.1.....q" "if."       "X0"        "NA." 

The documentation says:

A syntactically valid name consists of letters, numbers and the dot or underline characters and starts with a letter or the dot not followed by a number. <...> The character "X" is prepended if necessary. All invalid characters are translated to "."