do: Operating on Dataset Rows
In patperry/r-frame: Flexible Data Frames

Description Usage Arguments Details Value See Also Examples

Perform an action on each row in a dataset and combine the results.

do(x, f)
## Default S3 method:
do(x, f)
## S3 method for class 'dataset'
do(x, f)

`x`	a data object.
`f`	a function to perform on each row.

The do function calls code f using each row of x as a set of arguments. It then casts the result to a record with as.record and binds the records together into a dataset.

If x has no rows, then the result is NULL. Otherwise, the result is a dataset with the same keys as x with rows equal to the result of applying f to each row in x.

group, lapply.

# perform an action on each row
x <- dataset(n = 1:10)
do(x, function(n) 10 * n)

# named result
do(x, function(n) c(a = 10 * n))

# multiple results
do(x, function(n)
   record(a =  10 * n,
          b = -10 * n,
          c = "foo"))

# multiple columns
y <- dataset(count = c("one", "two", "three"),
             fruit = c("banana", "banana", "orange"))
do(y, function(c, f) c(fun = paste(c, f)))

# split into groups
x <- group(mtcars, gear, cyl)

# perform an action on each group
do(x, function(g)
   record(n    = nrow(g),
          mean = mean(g$mpg),
          sd   = sd(g$mpg)))