Insert rows in R based on a factor condition

Question

I'm attempting to run a rate-of-change calculation on a value column, but cannot due to;

1. A row is missing after each oil change due to a 'reset'.
2. My lack of R knowledge in inserting rows based on conditions.

This is my actual dataframe;

Before <- data.frame(
  Engine_ID = as.factor(c(1006,1006,1006,1006,1006,1006,1006)),
  Oil_Change = as.factor(c(1,0,1,1,0,0,0)),
  Value = c(5,6,3,7,9,11,12)
)

and this is what I need;

After <- data.frame(
  Engine_ID = as.factor(c(1006,1006,1006,1006,1006,1006,1006,1006,1006,1006)),
  Oil_Change = as.factor(c(1,NA,0,1,NA,1,NA,0,0,0)),
  Value = c(5,0,6,3,0,7,0,9,11,12)
)

Then I should be able to perform a true rate-of-change on the value column.

To do this, directly after each oil change (Oil_change == 1) I would like to insert a row of zero's.

Answer 1

Before$order <- 1:nrow(Before)

new <- Before[Before$Oil_Change == 1, ]
new$Oil_Change <- NA
new$Value <- 0

After <- rbind(Before, new)

After[order(After$order), ][ , -4]

   Engine_ID Oil_Change Value
1       1006          1     5
11      1006       <NA>     0
2       1006          0     6
3       1006          1     3
31      1006       <NA>     0
4       1006          1     7
41      1006       <NA>     0
5       1006          0     9
6       1006          0    11
7       1006          0    12