If the real problem is that R reads your data file and converts
everything it can into factors try including stringsAsFactors=FALSE
in your read.table (or similar) statement. I run into this often enough
that I set it as an option (I think it's:
options(stringsAsFactors=FALSE). Then you can do the conversion as
needed. Using as.numeric(as.character(f)) often changes values (due to
the whole factor/levels business).
... I also seem to remember read.table will let you pre-specify the data
type of each column.
Krzysztof
Uwe Ligges wrote:
From ?factor:
The interpretation of a factor depends on both the codes and the
"levels" attribute. Be careful only to compare factors with the same set
of levels (in the same order). In particular, as.numeric applied to a
factor is meaningless, and may happen by implicit coercion. To transform
a factor f to its original numeric values, as.numeric(levels(f))[f] is
recommended and slightly more efficient than as.numeric(as.character(f)).
Uwe Ligges
ojal john owino wrote:
Dear Users,
I have a variable in my dataset which is of type factor. But it actually
contains numeric entries which like 5.735 4.759 ..... This is because
the
data was read from a CSV file into R and this variable contained other
charaters which were not numeric. I have now dropped the records with the
characters which are not numeric for this variable and want to change
it to
numeric srotage type.
I have tried using as.numeric() function but it changes the values in the
variable to what I think are the ranks of the individual values of the
varible in the dataset. For example if 5.735 is the current content in
the
field, then the new object created by as.numeric will contain a value
like
680 if the 5.735 was the highest value for the varible and the dataset
had
680 records.
How can I change the storage type without changing the contents of this
variable in this case?
Thanks for your consideration.
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--
-----------------------------------------------
Krzysztof Sakrejda-Leavitt
Organismic and Evolutionary Biology
University of Massachusetts, Amherst
319 Morrill Science Center South
611 N. Pleasant Street
Amherst, MA 01003
work #: 413-325-6555
email: sakre...@nsm.umass.edu
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