[R] Conditionally adding a constant

[Rui Barradas]

Hello,

I believe this works.

f1 <- function(x){
	for(i in 2:length(x)) x[i] <- ifelse(x[i-1] > 3, x[i-1] + 2, x[i])
	x
}

f2 <- function(x){
	for(i in 2:length(x)) x[i] <- ifelse(is.na(x[i]) & (x[i-1] > 3), x[i-1] +
2, x[i])
	x
}

df <- data.frame(x = c(1,2,3,4,5), y = c(10,20,30,NA,NA))

apply(df, 2, f1)      # df$x[4] > 3, df$x[5] also changes
apply(df, 2, f2)      # only df$y has NA's

Maybe there's a better way, avoiding the loop.

Rui Barradas


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