CODEWITHSUNDEEP
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Elleni Toumpas
Elleni Toumpas

Reputation: 3

Check which cells (that hold lists) contains a certain value?

In R I would like to search each cell in a column, with the column containing a series of lists. I would like to return the index (or return T/F) for the cells that contain a certain value.

For example - I created this test dataframe. 

test <- data.frame(rows = 1:5, values = 0)
test$values <- list(1, c(2,3), c(4:6), 4, 0)

Attempting to query it using:

test[4 %in% test$values,]

In this example I would like to return the cells that contain the value 4 (so row 3 and 4 should be true). How do I do this? My current query returns just one TRUE as it is just testing the entire column (not each cell in that column).

I have in the past solved this using a for loop (roughly as below). eg: 

test$result <- FALSE
for (i in 1:nrow(test)){
    if (4 %in% test$values[i]){
        test$result[i] <- TRUE
    }
}

I don't really want this to be my solution each time I need to query like this.

Upvotes: 0

Views: 387

Answers (2)

Ronak Shah
Ronak Shah

Reputation: 388972

As it is a list you need to loop over it using sapply/lapply

test$result <- sapply(test$values, function(x) 4 %in% x)

test
#  rows  values result
#1    1       1  FALSE
#2    2    2, 3  FALSE
#3    3 4, 5, 6   TRUE
#4    4       4   TRUE
#5    5       0  FALSE

If you want to subset those rows you could do

test[sapply(test$values, function(x) 4 %in% x), ]

#  rows  values
#3    3 4, 5, 6
#4    4       4

Upvotes: 1

Marius
Marius

Reputation: 60070

The map functions in the purrr package are good for working with nested data like this:

purrr::map_lgl(test$values, ~ 4 %in% .)
[1] FALSE FALSE  TRUE  TRUE FALSE

Upvotes: 0

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