Easy way to iterate over a data frame and append multiple columns from a function returning a data frame

script.R

## An example of iterating over a data frame using the apply family and
## the tidyverse, appending multiple columns to a resultset.

library(tidyverse)
library(ggmap)

latLong <- data.frame(long= c(78.0422, -0.1246, 131.035904, 122.3493), 
                         lat = c(27.1750, 51.5007, -25.344646, 47.6205), 
                         name = c("Taj Mahal", "Big Ben", "Uluru", "Space Needle"))

## Address details are found by a reverse geocode lookup.
## The function returns a data frame.

results <- revgeocode(c(78.0422, 27.1750), output = "more")

## We want to return an arbitrarily large set of results
## by applying the function to the vectors containing 
## the latitude and longitude, writing the results
## back to the data frame.

## If we want to bring back a single value, we can use mapply.

getLocality <- function(long, lat) {
  locality <- revgeocode(c(long, lat), output = "more")
  locality <- locality$locality
  return(locality)
}

localities <- mapply(getLocality, latLong$long, latLong$lat)

## We can use the function to return the values to the data frame
## as a new column.

latLong$locality <- mapply(getLocality, latLong$long, latLong$lat)

## We can also use dplyr.

latLong <- latLong %>%
  rowwise() %>%
  mutate(dplyrLocality = getLocality(long, lat))

## What about if we want to write back all of the result set?

getAddress <- function(long, lat) {
  address <- revgeocode(c(long, lat), output = "more")
  return(address)
}

## What is the best way to write the whole data frame back to the
## latLong data frame as multiple new columns? We can use the map2_df
## function from the purrr package, which returns a data frame.

df <- map2_df(latLong$long, latLong$lat, getAddress)
result <- data.frame(latLong,df)

## Copy the script into your R console and try it out!