suffix | use when |
---|---|
_all | you want to apply the verb to all columns |
_at | you want to apply the verb to specified columns |
_if | you want to apply the verb to all the columns with some property |
mutate()
, summarize()
, select()
, and rename()
Verb | Example | Example explanation |
---|---|---|
summarize_all | summarize_all(mean) | finds the mean of all variables |
summarize_at | summarize_at(vars(x, y), mean) | finds the mean of variables x and y |
summarize_if | summarize_if(is.double, mean) | finds the mean of all double variables |
mutate_all | mutate_all(as.character) | converts all variables to characters |
mutate_at | mutate_at(vars(x, y), as.character) | converts variables x and y to characters |
mutate_if | mutate_if(is.factor, as.character) | converts all factor variables to characters |
rename_all | rename_all(str_to_lower) | changes all column names to lowercase |
rename_at | rename_at(vars(X, Y), str_to_lower) | changes the names of columns X and Y to x and y |
rename_if | rename_if(is.double, str_to_lower) | changes the names of double columns to lowercase |
select_all | select_all(str_to_lower) | selects all columns and changs their names to lowercase (better to use rename_all()) |
select_at | select_at(vars(X, Y), str_to_lower) | selects just columns X and Y and changes their names to x and y |
select_if | select_if(is.double, str_to_lower) | selects just double columns and changes their names to lowercase |
verb | example | example_explanation |
---|---|---|
summarize_if | summarize_if(is.double, mean, na.rm = TRUE) | finds the mean, excluding NAs, of all double variables |
summarize_all | summarize_all(mean, trim = 0.1, na.rm = TRUE) | finds the mean of all variables, exluding NAs. Removes the bottom and top 10% of values of each variable before computing mean |
verb | example | example_explanation |
---|---|---|
summarize_all | summarize_all(~ sum(is.na(.))) | determines the number of NAs in each column |
select_if | select_if(~ n_distinct(.) > 1) | selects only the columns with more than one distinct value |
filter()
verb | example | example_explanation |
---|---|---|
filter_all | filter_all(all_vars(!is.na(.)) | finds rows without any NAs |
filter_all | filter_all(any_vars(!is.na(.)) | finds rows with at least one non-NA value |
filter_at | filter_at(vars(x, y), all_vars(!is.na(.)) | finds rows where both x and y are non-NA |
filter_at | filter_at(vars(x, y), any_vars(!is.na(.)) | finds rows where at least one of x and y is non-NA |
filter_if | filter_if(is.double, all_vars(!Is.na(.)) | finds rows where all double variables are non-NA |
filter_if | filter_if(is.double, any_vars(!Is.na(.)) | finds rows where at least one double variable is non-NA |