R help - Sep 2003 - How do I coerce numeric factor columns of data frame to vector?

I have just noticed that quite a few columns of a data frame that I am 
working on are numeric factors. For summary() purposes I want them to be 
vectors. I tried, for example

 > indx <- c(1:18,21:37,40,41)
 > i <- 0
 > i <- i+1
 > summary(as.vector(sflows1[indx[i]]))
            Length Class  Mode
min.pkt.sz 3000   factor numeric

but this does not give the five-number summary that I want. I know that 
I can go back and modify read.table() to change the class of the 
columns, but I want to change the frame without re-reading it.

Murray

-- 
Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
Department of Statistics, University of Waikato, Hamilton, New Zealand
Email: maj at waikato.ac.nz                                Fax 7 838 4155
Phone  +64 7 838 4773 wk    +64 7 849 6486 home    Mobile 021 1395 862

>>>>> "Murray" == Murray Jorgensen <maj at
stats.waikato.ac.nz> writes:
    > I have just noticed that quite a few columns of a data
    > frame that I am working on are numeric factors. For
    > summary() purposes I want them to be vectors.

Do you want them to be vectors or do you want numeric values?  If
the later, try as.numeric instead of as.vector:
> as.vector(factor(rep(seq(4),3)))
 [1] "1" "2" "3" "4" "1"
"2" "3" "4" "1" "2"
"3" "4"
> as.numeric(factor(rep(seq(4),3)))
 [1] 1 2 3 4 1 2 3 4 1 2 3 4
> summary(as.vector(factor(rep(seq(4),3))))
   Length     Class      Mode 
       12 character character 
> summary(as.numeric(factor(rep(seq(4),3))))
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
   1.00    1.75    2.50    2.50    3.25    4.00 


Mike

Murray  -

Suppose your data frame is called  mydata.  If ALL of the columns were
factors with numeric levels, you could do:

newdata <- as.data.frame(lapply(mydata, function(x)
as.numeric(as.character(x))))

(Sorry about the nested functions.  I didn't invent these complications.)
When only the columns listed in  indx  need to be converted, make a
complementary vector  indy <- c(19,20,38,39,42:60)  (say), then do

newdata <- as.data.frame(lapply(mydata[indx],
                     function(x) as.numeric(as.character(x))))
alldata <- c(mydata[indy], newdata)[ sort.list(c(indy, indx)) ]

Again, it's just a trick to get the columns back in the original order,
but I think my code above will do it.  Best luck.  Others will probably
have more elegant solutions.

-  tom blackwell  -  u michigan medical school  -  ann arbor  -

On Tue, 9 Sep 2003, Murray Jorgensen wrote:
> I have just noticed that quite a few columns of a data frame that I am
> working on are numeric factors. For summary() purposes I want them to be
> vectors. I tried, for example
>
>  > indx <- c(1:18,21:37,40,41)
>  > i <- 0
>  > i <- i+1
>  > summary(as.vector(sflows1[indx[i]]))
>             Length Class  Mode
> min.pkt.sz 3000   factor numeric
>
> but this does not give the five-number summary that I want. I know that
> I can go back and modify read.table() to change the class of the
> columns, but I want to change the frame without re-reading it.
>
> Murray
>
> --
> Dr Murray Jorgensen      http://www.stats.waikato.ac.nz/Staff/maj.html
> Department of Statistics, University of Waikato, Hamilton, New Zealand
> Email: maj at waikato.ac.nz                                Fax 7 838 4155
> Phone  +64 7 838 4773 wk    +64 7 849 6486 home    Mobile 021 1395 862
>
> ______________________________________________
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>