Loop over a list

Loop directly over the nyc list (loop version 1). Define a looping index and do subsetting using double brackets (loop version 2).

nyc <- list(pop = 8405837, 
            boroughs = c("Manhattan", "Bronx", "Brooklyn", "Queens", "Staten Island"), 
            capital = FALSE)

Loop version 1

for (i in nyc){
  print(i)
}

## [1] 8405837
## [1] "Manhattan"     "Bronx"         "Brooklyn"      "Queens"       
## [5] "Staten Island"
## [1] FALSE

Loop version 2

for (i in 1:length(nyc)){
  print(nyc[[i]])
  }

## [1] 8405837
## [1] "Manhattan"     "Bronx"         "Brooklyn"      "Queens"       
## [5] "Staten Island"
## [1] FALSE

Notice that you need double square brackets - [[ ]] - to select the list elements in loop version 2.