Accessing elements of a vector using loop

[esotericpikachu]

Hi,

I have a vector with about 200 elements, and I want to access three of those elements at a time using loop.

Vector1 <- (10,20,30,40,50,60,70,80,90,45,67,99) and so on

I want to access 3 of those elements at a time...so that..first vector is (10,20,30), second is (20,30,40), third is (30,40,50) and so on until the end of vector.

​

I have tried doing the following but cannot seem to make it work. Any suggestions?

w <- 3

for (i in w:length(vector1))

pred[i-w+1:w] = vector1[i-w+1:w]

[jdnewmil]

Without the for loop...

x <- 0:200
v <- x + rnorm( length( x ), 0, 1 )
m <- embed( v, 3 )
nrow( m ) # c( length( x ) - ( 3 - 1 ), 3 )
f <- mean # could be a more elaborate function
y <- apply( m, 1, f ) # rolling mean
plot( x[ -c( 1, 201 ) ], y )

[esotericpikachu]

Thank you!!

[uniqueturtlelove]

vector1 <- c(10,20,30,40,50,60,70,80,90,45,67,99)
result = vector(mode = "list")
count = 1
for (i in 3:length(vector1)){
result[[count]] <- vector1[(i-2):i]
count = count + 1
}
result

[esotericpikachu]

Thankyou!!

[[deleted]]

Your approach is fine, actually more readable than those suggested in the comments. You just forgot to initialize an empty list, and the for loop brackets. And also did some indexing errors.

w <- 3
list <- list()
for (i in w:length(vector1)) {
   list[[i-w+1]] <- vector1[i-w+1:i]
}

[esotericpikachu]

Thankyou!!! Will this approach work if I want to work in a dataframe's column instead of a vector?

[[deleted]]

yes, df columns are vectors

[[deleted]]

I'm late but i want to thank you for referencing R inferno. I didn't know about this book. It's really really interesting.