Selecting only numeric columns from a data frame

Question

Suppose  you have a data frame like this    x  lt - data frame v1 1 20 v2 1 20 v3 1 20 v4 letters 1 20     How would you select only those columns in x that are numeric

User · Answer

If you have many factor variables  you can use select if funtion  install the dplyr packages  There are many function that separates data by satisfying a condition  you can set the conditions   Use like this   categorical lt -select if df is factor  str categorical

User · Answer

Filter   from the base package is the perfect function for that use-case  You simply have to code    Filter is numeric  x    It is also much faster than select if     library microbenchmark  microbenchmark      dplyr  select if mtcars  is numeric       Filter is numeric  mtcars      returns  on my computer  a median of 60 microseconds for Filter  and 21 000 microseconds for select if  350x faster

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Numerical variables  lt - which sapply df  is numeric     then extract column names  Names  lt - names Numerical variables

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in case you are interested only in column names then use this    names dplyr  select if train is numeric

User · Answer

iris   gt   dplyr  select where is numeric    as per most recent updates  Another option with purrr would be to negate discard function  iris   gt   purrr  discard   is numeric      If you want the names of the numeric columns  you can add names or colnames  iris   gt   purrr  discard   is numeric       gt   names

User · Answer

This an alternate code to other answers   x   sapply x  class      numeric     with a data table  x   lapply x  is numeric     TRUE  with   FALSE

User · Answer

EDIT  updated to avoid use of ill-advised sapply  Since a data frame is a list we can use the list-apply functions  nums  lt - unlist lapply x  is numeric      Then standard subsetting x    nums      don t use sapply  even though it s less code    nums  lt - sapply x  is numeric   For a more idiomatic modern R I d now recommend x    purrr  map lgl x  is numeric    Less codey  less reflecting R s particular quirks  and more straightforward  and robust to use on database-back-ended tibbles  dplyr  select if x  is numeric   Newer versions of dplyr  also support the following syntax  x   gt   dplyr  select where is numeric

User · Answer

library purrr  x  lt - x   gt   keep is numeric

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This doesn t directly answer the question but can be very useful  especially if you want something like all the numeric columns except for your id column and dependent variable    numeric cols  lt - sapply dataframe  is numeric    gt   which   gt                       names   gt   setdiff    c  id variable    dep var     dataframe   lt  gt   dplyr  mutate at numeric cols  function x  your function x

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Another way could be as follows -   extracting numeric columns from iris datset  iris sapply iris  is numeric

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The dplyr package s select if   function is an elegant solution   library  dplyr   select if x  is numeric

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The library PCAmixdata has functon splitmix that splits quantitative Numerical data  and qualitative  Categorical data  of a given dataframe  YourDataframe  as shown below    install packages  PCAmixdata   library PCAmixdata  split  lt - splitmix YourDataframe  X1  lt - split X quanti Gives numerical columns in the dataset   X2  lt - split X quali  Gives categorical columns in the dataset

[r] Selecting only numeric columns from a data frame

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