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R For Loop
For Loops
A for loop is used for multiplication in sequence:
Example
print(x)
}
This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages.
With a for loop we can create a set of statements, once per object in vector, matching members, lists, etc ..
Example
Print every item in a list:
for (x in fruits) {
print(x)
}
Example
Print the number of dices:
for (x in dice) {
print(x)
}
The for loop does not require variable indexing to be pre-configured, such as for while loops.
Break
With a break statement, we can stop the loop before it goes into all items:
Example
Stop the loop at "cherry":
for (x in fruits) {
if (x == "cherry") {
break
}
print(x)
}
The loop will stop at "cherry" because we chose to end the loop using a break statement where x is equal to "cherry" (x == "cherry").
Next
With the next statement, we can skip repeats without breaking the loop:
Example
Skip "banana":
for (x in fruits) {
if (x == "banana") {
next
}
print(x)
}
When the loop passes the "banana", it will jump and continue the loop.
Yahtzee!
If .. Else Combined with a For Loop
To illustrate a practical example, suppose we are playing a game of Yahtzee!
Example
Print "Yahtzee!" If the dice number is 6:
for(x in dice) {
if (x == 6) {
print(paste("The dice number is", x, "Yahtzee!"))
} else {
print(paste("The dice number is", x, "Not Yahtzee"))
}
}
When the loop reaches values from 1 to 5, it prints "No Yahtzee" and its number. When it reaches a value of 6, it prints "Yahtzee!" and its number.
Nested Loops
You can also have a loop inside the loop:
Example
Print the adjective of each fruit in a list:
fruits <- list("apple", "banana", "cherry")
for (x in adj) {
for (y in fruits) {
print(paste(x, y))
}
}