Looping over multiple lists with base R

Question

In python we can do this..

numbers = [1, 2, 3]
characters = ['foo', 'bar', 'baz']

for item in zip(numbers, characters):
    print(item[0], item[1])

(1, 'foo')
(2, 'bar')
(3, 'baz')

We can also unpack the tuple rather than using the index.

for num, char in zip(numbers, characters):
    print(num, char)

(1, 'foo')
(2, 'bar')
(3, 'baz')

How can we do the same using base R?

Answer 1

To do something like this in an R-native way, you'd use the idea of a data frame. A data frame has multiple variables which can be of different types, and each row is an observation of each variable.

d <- data.frame(numbers = c(1, 2, 3),
                characters = c('foo', 'bar', 'baz'))
d
##   numbers characters
## 1       1        foo
## 2       2        bar
## 3       3        baz

You then access each row using matrix notation, where leaving an index blank includes everything.

d[1,]
##   numbers characters
## 1       1        foo

You can then loop over the rows of the data frame to do whatever you want to do, presumably you actually want to do something more interesting than printing.

for(i in seq_len(nrow(d))) {
  print(d[i,])
}
##   numbers characters
## 1       1        foo
##   numbers characters
## 2       2        bar
##   numbers characters
## 3       3        baz