For loop

Intermediate R

Filip Schouwenaars

DataCamp Instructor

for loop

for(var in seq) {
  expr
}

cities <- c("New York", "Paris", 
            "London", "Tokyo",              
            "Rio de Janeiro", "Cape Town")
cities

"New York"   "Paris"  ...  "Cape Town"

for loop

for(var in seq) {
  expr
}

cities <- c("New York", "Paris", 
            "London", "Tokyo",              
            "Rio de Janeiro", "Cape Town")

for(var in seq) {
  expr
}

for loop

for(var in seq) {
  expr
}

cities <- c("New York", "Paris", 
            "London", "Tokyo",              
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  expr
}

for loop

for(var in seq) {
  expr
}

cities <- c("New York", "Paris", 
            "London", "Tokyo",              
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  print(city)
}

for loop

for(var in seq) {
  expr
}

cities <- c("New York", "Paris", 
            "London", "Tokyo",              
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  print(city)
}

"New York"

for loop

for(var in seq) {
  expr
}

cities <- c("New York", "Paris", 
            "London", "Tokyo",              
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  print(city)
}

"Paris"

for loop

cities <- c("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  print(city)
}

"New York"
"Paris"
"London"
"Tokyo"
"Rio de Janeiro"
"Cape Town"

for loop over list

cities <- list("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  print(city)
}

"New York"
"Paris"
"London"
"Tokyo"
"Rio de Janeiro"
"Cape Town"

break statement

cities <- list("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  if(nchar(city) == 6) {
    break
  }
  print(city)
}

break statement

cities <- list("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  if(nchar(city) == 6) {
    break
  }
  print(city)
}

"New York"

"Paris"

next statement

cities <- list("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  if(nchar(city) == 6) {
    next
  }
  print(city)
}

"New York"
"Paris"
"Tokyo"
"Rio de Janeiro"
"Cape Town"

for loop: v2

cities <- c("New York", "Paris", 
            "London", "Tokyo",            
            "Rio de Janeiro", "Cape Town")

for(city in cities) {
  print(city)
}

for loop: v2

cities <- c("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

for(i in 1:length(cities)) {
  print(city)
}

for loop: v2

cities <- c("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

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

"New York"
"Paris"
"London"
"Tokyo"
"Rio de Janeiro"
"Cape Town"

for loop: v2

cities <- c("New York", "Paris", 
            "London", "Tokyo", 
            "Rio de Janeiro", "Cape Town")

for(i in 1:length(cities)) {
  print(paste(cities[i], "is on position", 
              i, "in the cities vector."))
}

"New York is on position 1 in the cities vector."
"Paris is on position 2 in the cities vector."
"London is on position 3 in the cities vector."
"Tokyo is on position 4 in the cities vector."
"Rio de Janeiro is on position 5 in the cities vector."
"Cape Town is on position 6 in the cities vector."

for loop: wrap-up

cities <- c("New York", "Paris", 
            "London", "Tokyo",
            "Rio de Janeiro", "Cape Town")

#Concise, easy to read, but no access to looping index
for(city in cities) {
  print(city)
}

#Harder to read and write, but more versatile
for(i in 1:length(cities)) {
  print(cities[i])
}

Let's practice!

Intermediate R