R - Perform two calculations to different parts of a loop - r

Question

Ok so I have written a loop which intends to for the first part of the loop, perform a multiplication calculation, multiplying two columns. Afterwards, for the remainder of the loop the loop is to perform another multiplication using two different columns than the first.
The columns for multiplation are: ocret and clret which multiply against response.
My code for this:
train.set$output[[1]] = if (train.set$response[[1]] == 1) {
apply(train.set[,c('ocret', 'response')], 1, function(x) { (x[1]*x[2])} )
}
for (i in 2:nrow(train.set)){
train.set$output[i] = if(train.set$response[i] == 1) {
apply(train.set[,c('clret', 'response')], 1, function(x) { (x[1]*x[2])})
train.set$output[i-1]
}
}
The idea for this was first finding a response == 1, it was to perform the ocret * response calculation.
For the second part of the loop, it was to start on row 2 as to not overwrite the first part... and continue to loop down the +1 and perform the clret * response calculation.
The logic makes sense to me, this is pretty much my first attempt at a loop. When I run the code, nothing happens, it doesnt make the output column, can anyone give me any pointers? I continue to read it and it makes sense, not sure what im missing, any explanation greatly appreciated.
Example data frame and output below:
ocret clret response output
1 0.00730616 0.003382433 0 0
2 -0.084899894 -0.088067766 0 0
3 0.047208568 0.054174679 1 0.047208568
4 -0.002671414 -0.004543992 0 0
5 -0.039943462 -0.040290793 0 0
6 -0.01428499 -0.013506524 0 0
7 -0.037054965 -0.038517845 0 0
8 -0.058027611 -0.057394837 1 -0.058027611
9 -0.004014491 -0.011332705 1 -0.011332705
10 -0.079419682 -0.076167096 1 -0.076167096
11 -0.003424577 -0.011759287 1 -0.011759287
12 0.099260455 0.115800375 1 0.115800375
13 -0.011841897 -0.005322141 1 -0.005322141
14 -0.087230999 -0.090349775 1 -0.090349775
15 0.040570359 0.042507445 1 0.042507445
16 -0.001846555 -0.006212821 1 -0.006212821
17 0.044398056 0.047684898 1 0.047684898
18 -0.025856823 -0.030799705 0 0
19 -0.057677505 -0.061012471 0 0
20 0.010043567 0.012634046 0 0
21 -0.020609404 -0.034511205 0 0
Line 3: ocret * response
Line 8: ocret * response
Line 9 to 16: clret * response

Answer 1

For loop may not be required. We can use dplyr and data.table to get the desired output (dt2).
library(dplyr)
library(data.table)
dt2 <- dt %>%
mutate(RunID = rleid(response)) %>%
group_by(RunID) %>%
mutate(output = ifelse(response == 0, 0,
ifelse(row_number() == 1, ocret, clret))) %>%
ungroup() %>%
select(-RunID)
Data Preparation
dt <- read.table(text = " ocret clret response
1 0.00730616 0.003382433 0
2 -0.084899894 -0.088067766 0
3 0.047208568 0.054174679 1
4 -0.002671414 -0.004543992 0
5 -0.039943462 -0.040290793 0
6 -0.01428499 -0.013506524 0
7 -0.037054965 -0.038517845 0
8 -0.058027611 -0.057394837 1
9 -0.004014491 -0.011332705 1
10 -0.079419682 -0.076167096 1
11 -0.003424577 -0.011759287 1
12 0.099260455 0.115800375 1
13 -0.011841897 -0.005322141 1
14 -0.087230999 -0.090349775 1
15 0.040570359 0.042507445 1
16 -0.001846555 -0.006212821 1
17 0.044398056 0.047684898 1
18 -0.025856823 -0.030799705 0
19 -0.057677505 -0.061012471 0
20 0.010043567 0.012634046 0
21 -0.020609404 -0.034511205 0",
header = TRUE, stringsAsFactors = FALSE)