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R: Subsetting a list based on a condition

Quite a handy couple of lines of code to subset a list in R to just those elements which meet a certain condition. Here’s an example to return only those elements of a list which are a certain class.

Thanks to this StackOverflow answer.


list.condition <- sapply(input.list, function(x) class(x)=="desired.class")
output.list  <- input.list[list.condition]
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Discussion

5 thoughts on “R: Subsetting a list based on a condition

  1. As I just posted to the StackOverflow thread, this is what the Filter() function was made for. Also, you may want to avoid using `==’ to test for an object’s class. Check out inherits() — much more robust.

    Posted by Jason | January 20, 2012, 12:44 am
  2. Another option is the subset() function.

    Posted by Ken | January 26, 2012, 1:19 am
    • Hi Ken

      Does subset work with lists? From the documentation, it looks like it only works with vectors, matrices or data frames. Also, I’m trying to get more into the [] notation as I’m a big user of subset.

      Cheers

      Mark

      Posted by markbulling | January 26, 2012, 8:10 pm

Trackbacks/Pingbacks

  1. Pingback: Filtering a list with the Filter higher-order function | Left Censored - January 27, 2012

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