Hi Alina,
On Tue, Jun 21, 2011 at 4:38 PM, Alina Sheyman <alina...@gmail.com> wrote:
> I'm trying to convert data from character to numeric.
>
> I've imported data as a csv file, I'm assuming that the import is a
> database - are all the columns in a database considered "vectors" and that
> they can be operated on individually
> Therefore I've tried the following
> mydata <- as.numeric(mydata$apples)
The term is data frame, not database. You don't tell us how you
imported the data - read.table()? read.csv()? Using what options?
You are right that each column can be operated on individually.
Are you certain that every element in mydata$apples is numeric? If it
were, read.table() wouldn't import it as character, but as numeric.
What does
str(mydata)
show?
> when i then look at mydata again the named column is still in "character"
> format
How did you determine that?
> if i do mydata2 <- as.numeric(mydata$apples)
> the new object mydata2 is empty.
This perplexes me; it means that R can't identify ANY of the
information in your column as numeric. If some were numeric and some
character, you would get a warning and the character values would be
replaced with NA.
> vec1 <- c("1", "2", "3")
> as.numeric(vec1)
[1] 1 2 3
> vec1 <- c("1", "2", "3", "a")
> as.numeric(vec1)
[1] 1 2 3 NA
Warning message:
NAs introduced by coercion
Are you certain that "apples" is the correct column name? R is case-sensitive.
> Am i missing something about the structure of R?
>
It's hard to tell. You are certainly missing a lot of the information
we need to answer your question.
Sarah
--
Sarah Goslee
http://www.functionaldiversity.org
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