[R] Extracting Numeric Columns from Data Fram

[Henrik Pärn]

Dear Barry,


I saw that you received several nice answers on how to 'pull out' numeric columns. You also wrote that an alternative could be to 'just operate only on' numerics. Here is one possibility:

library(plyr)

# some dummy data
df <- data.frame(nonnum1 = letters[1:5], num1 = 1:5, nonnum2 = letters[6:10], num2 = rnorm(5)) 


# operate only on numeric variables
numcolwise(.fun = mean)(df)

# or only on 'discrete' variables (following the terminology on ?colwise)
catcolwise(.fun = toupper)(df)


Best regards,

Henrik



Hello,





I've got a data frame with a mix of numeric, integer and factor columns.


I'd like to pull out (or just operate only on) the numeric/integer columns.


Every thing I've found in searches is about how to subset by rows,


or how to operate assuming you have the column names.? I'd like to pull


by type.





Thanks!





Barry


--

Henrik Pärn
Centre for Conservation Biology
Department of Biology
Norwegian University of Science and Technology
NO-7491 Trondheim
NORWAY

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