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Can someone recommend a function that can allow me to count and return the number of items in a list?
library(stringr) l <- strsplit(words, "a") if(# number of items in list l < 1) next 
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To get length of list in R programming, call length() function and pass the list as argument to length function. The length function returns an integer representing the number of items in the list.
To count occurrences between columns, simply use both names, and it provides the frequency between the values of each column. This process produces a dataset of all those comparisons that can be used for further processing.
count() lets you quickly count the unique values of one or more variables: df %>% count(a, b) is roughly equivalent to df %>% group_by(a, b) %>% summarise(n = n()) .
length(x)
Get or set the length of vectors (including lists) and factors, and of any other R object for which a method has been defined.
lengths(x)
Get the length of each element of a list or atomic vector (is.atomic) as an integer or numeric vector.
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Advice for R newcomers like me : beware, the following is a list of a single object :
> mylist <- list (1:10) > length (mylist) [1] 1 In such a case you are not looking for the length of the list, but of its first element :
> length (mylist[[1]]) [1] 10 This is a "true" list :
> mylist <- list(1:10, rnorm(25), letters[1:3]) > length (mylist) [1] 3 Also, it seems that R considers a data.frame as a list :
> df <- data.frame (matrix(0, ncol = 30, nrow = 2)) > typeof (df) [1] "list" In such a case you may be interested in ncol() and nrow() rather than length() :
> ncol (df) [1] 30 > nrow (df) [1] 2 Though length() will also work (but it's a trick when your data.frame has only one column) :
> length (df) [1] 30 > length (df[[1]]) [1] 2 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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