[R] discarding 'levels'

[Mike Nielsen]

>From TFM of read.table:

 as.is: the default behavior of 'read.table' is to convert character
          variables (which are not converted to logical, numeric or
          complex) to factors.  The variable 'as.is' controls the
          conversion of columns not otherwise specified by
          'colClasses'. Its value is either a vector of logicals
          (values are recycled if necessary), or a vector of numeric or
          character indices which specify which columns should not be
          converted to factors.

You may have some blanks in the third column.

Factor levels whose character representation happens to be a numeral
don't necessarily compare equal to the integer with the same character
representation (if you get my drift...).

You can use "as.numeric", but better would be to use colClasses in read.table.

Regards,

Mike

On 10/4/06, hoopz <zwhedbee at hotmail.com> wrote:
>
> Ok, so I am using read.table to read a .txt file and put it into a matrix.
> There are some values that are 'NA'.  If I use read.table with as.is =FALSE,
> then some of the entries in the matrix return this:
>
> > data[1,3]
> [1]  0
> Levels:  0  1  NA
>
> and if I do
>
> > data[1,3]==0
>
> it returns FALSE.  It's a zero, it's not false!
>
>
> If I set as.is=TRUE, I don't get the levels problem, but in those entries
> where I did get the levels problem, this happens:
>
> > data[1,3]
> [1] " 0"
>
> This time, it keeps it as a string.  I can use as.numeric to fix it now, but
> I'm just curious as to why this happens.
>
>
> Thanks
> --
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-- 
Regards,

Mike Nielsen