[R] How to more efficently read in a big matrix

[Gabor Grothendieck]

On Nov 10, 2007 12:19 AM, affy snp <affysnp at gmail.com> wrote:
> Thanks Jim.
>
> I tried:
>
> A<-read.table(file="243_47mel_withnormal_expression_log2.txt",
> +header=TRUE,row.names=1,colClasses=c('factor', rep('numeric',486)))
>
> by specifying colClass but it did not work.
>
> The error message I got is:
>
> > A<-read.table(file="243_47mel_withnormal_expression_log2.txt",header=TRUE,row.names=1,colClasses=c('factor', rep('numeric',486)))
> Error in scan(file, what, nmax, sep, dec, quote, skip, nlines, na.strings,  :
>  scan() expected 'a real', got 'B'
>

That's because you have only specified 487 variables to colClasses but
there are
actually 488 variables since the row names count.  See the colClasses entry of
?read.table where it is explained.