I have just started learning R and I wrote this code to learn on functions and loops.
squared<-function(x){
m<-c()
for(i in 1:x){
y<-i*i
c(m,y)
}
return (m)
}
squared(5)
NULL
Why does this return NULL. I want i*i
values to append to the end of m
and return a vector. Can someone please point out whats wrong with this code.
You haven't put anything inside m <- c()
in your loop since you did not use an assignment. You are getting the following -
m <- c()
m
# NULL
You can change the function to return the desired values by assigning m
in the loop.
squared <- function(x) {
m <- c()
for(i in 1:x) {
y <- i * i
m <- c(m, y)
}
return(m)
}
squared(5)
# [1] 1 4 9 16 25
But this is inefficient because we know the length of the resulting vector will be 5 (or x
). So we want to allocate the memory first before looping. This will be the better way to use the for()
loop.
squared <- function(x) {
m <- vector("integer", x)
for(i in seq_len(x)) {
m[i] <- i * i
}
m
}
squared(5)
# [1] 1 4 9 16 25
Also notice that I have removed return()
from the second function. It is not necessary there, so it can be removed. It's a matter of personal preference to leave it in this situation. Sometimes it will be necessary, like in if()
statements for example.
I know the question is about looping, but I also must mention that this can be done more efficiently with seven characters using the primitive ^
, like this
(1:5)^2
# [1] 1 4 9 16 25
^
is a primitive function, which means the code is written entirely in C and will be the most efficient of these three methods
`^`
# function (e1, e2) .Primitive("^")
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With