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Q: changing the class of an object

3 messages · Dave Evens, Bert Gunter, Uwe Ligges

Dave Evens
# 
Dear All,

I have a list of dataframes, each cell in every
dataframe (after I have cleaned up the dataframes) is
either real or NA  but have class character (I think).
I would like to know how to change the class of every
cell without using a for-loop. I currently have this

dataframes <- sapply(1: no.of.subs, function(k)
apply(dataframes[[k]], 2, function(x) {         
if(class(x)=="character") x <- as(x, "numeric"); x }))

but this neither changes the cells to numeric nor
keeps the dataframes in a list.

It creates one dataframe with number of rows=(no of
rows in a dataframe*no of colums) and number of
columns = no.of.subs

Can someone please help? Thanks in advance for any
help.

Dave
Bert Gunter
# 
Datadrames don't have "cells" -- class, type, etc. is determined on a column
by column basis (which is the same as a component by component basis, since
datframes are also lists) Please read "An Introduction to R" before
proceeding and posting so that you understand R's basic data structures and
conventions.

BTW -- what do you have against for loops? One should vectorize calculations
whenever possible,of course, but for loops are often useful and essentially
instantaneous. 

-- Bert Gunter
Genentech Non-Clinical Statistics
South San Francisco, CA
 
"The business of the statistician is to catalyze the scientific learning
process."  - George E. P. Box
Uwe Ligges
#
Dave Evens wrote:

            

      
      
      
    

        
what is a cell?

            

      
      
      
    

        
A simple way is

   data.frame(sapply(X, as.numeric))

but I guess the real problem is some steps before. You should take a 
look why you got character vectors in your data.frame rather than 
numeric ones.

Uwe Ligges