Merging 2 Vectors to 1 Vector that satisfies certain criteria

user_17190585 0
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I have two vectors that can be written as follows:

aa <- c(0, 0, 0, 0, 1, 0, 0, 0)
bb <- c(0, 2, 0, 0, 3, 1, 1, 1)

I want to merge these vectors such that the rest of vector bb takes the value zero when vector aa interfere with the value 1. In this example the result should look like:

cc <- c(0, 2, 0, 0, 3, 0, 0, 0)

What is the fastest and most efficient way to do this in R?

vector r
2 Answers

We may do

library(dplyr)
ifelse(lag(cummax(aa), default = 0) == 0, bb, aa)
[1] 0 2 0 0 3 0 0 0

Or another way is

bb * !c(0, head(cummax(aa), -1))
[1] 0 2 0 0 3 0 0 0

Or another option

ind <- (which.max(aa) + 1):length(aa)
bb[ind] <- aa[ind]
> bb
[1] 0 2 0 0 3 0 0 0
user_37322710

This is maybe too much for this task. At least for me it is easier to follow:

library(dplyr)
cc <- tibble(aa,bb) %>% 
  group_by(id_group=lag(cumsum(aa==1), default = 0)) %>% 
  mutate(cc = ifelse(id_group == 0, coalesce(bb,aa), coalesce(aa,bb))) %>% 
  pull(cc)

output:

[1] 0 2 0 0 3 0 0 0
user_133216470
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