[Rd] write.table

[Prof Brian Ripley]

On Wed, 6 Dec 2000, Torsten Hothorn wrote:

> 
> Good morning, 
> 
> suppose the following:
> 
> m <- round(matrix(rnorm(16), ncol=4), 3)
> a <- rev(c(0.01, 0.025, 0.05, 0.1))
> rownames(m) <- a
> colnames(m) <- c("0.25,0.75", "0.4,0.6", "0.1,0.9", "0.4,0.9")
> m
>       0.25,0.75 0.4,0.6 0.1,0.9 0.4,0.9
> 0.1       1.034  -0.119  -1.213   0.619
> 0.05      0.035   1.074   0.525   1.671
> 0.025    -1.687   0.960   0.324  -0.170
> 0.01      0.906   1.642   0.557  -2.224
> 
> and now write.table says:
> 
> write.table(m)
> "X0.25.0.75" "X0.4.0.6" "X0.1.0.9" "X0.4.0.9"
> "0.1" "1.034" "-0.119" "-1.213" "0.619"
> "0.05" "0.035" "1.074" "0.525" "1.671"
> "0.025" "-1.687" "0.96" "0.324" "-0.17"
> "0.01" "0.906" "1.642" "0.557" "-2.224"
> 
> If one writes 'm' into a file and reads it using read.table:
> 
> read.table("dummy")
>       X0.25.0.75 X0.4.0.6 X0.1.0.9 X0.4.0.9
> 0.1        1.034   -0.119   -1.213    0.619
> 0.05       0.035    1.074    0.525    1.671
> 0.025     -1.687    0.960    0.324   -0.170
> 0.01       0.906    1.642    0.557   -2.224
> 
> the colnames are incorrect. Do I miss something?

Yes.  write.table converts to a data frame. Try

x <- data.frame(m, check.names=FALSE)
write.table(x)

to give it a data frame in the first place.  The help says:

       x: the object to be written, typically a data frame.  If not, it
          is attempted to create one from it.

and the names get converted during that process to valid names.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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