Search in a column based on the value of a different column - r

Question

I have a simple table with three columns ("Year", "Target", "Value") and I would like to create a new column (Resp) containing the "Year" where "Value" is higher than "Target". The select value (column "Year") correspond to the first time that "Value" is higher than "Target".
This is part of the table:
db <- data.frame(Year=2010:2017, Target=c(3,5,2,7,5,8,3,6), Value=c(4,5,2,7,4,9,5,8)).
print(db)
Yea Target Value
1 2010 3 4
2 2011 5 5
3 2012 2 2
4 2013 7 3
5 2014 5 4
6 2015 8 9
7 2016 3 5
8 2017 6 8
The pretended result is:
Year Target Value Resp
1 2010 3 4 2011
2 2011 5 5 2015
3 2012 2 2 2013
4 2013 7 3 2015
5 2014 5 4 2015
6 2015 8 9 NA
7 2016 3 5 2017
8 2017 6 8 NA
Any suggestion how can I solve this problem?
In addition to the 'Resp' column, I want to create a new one (Black.Y) containing the "Year" corresponding to the minimum of "Value" until 'Value' is higher than "Target".
The pretended result is:
Year Target Value Resp Black.Y
1 2010 3 4 2011 NA
2 2011 5 5 2015 2012
3 2012 2 2 2013 NA
4 2013 7 3 2015 2014
5 2014 5 4 2015 NA
6 2015 8 9 NA 2016
7 2016 3 5 2017 NA
8 2017 6 8 NA NA
Any suggestion how can I solve this problem?

Answer 1

Here's an approach in base R:
o <- outer(db$Target, db$Value, `<`) # compute a logical matrix
o[lower.tri(o, diag = TRUE)] <- FALSE # replace lower.tri and diag with FALSE
idx <- max.col(o, ties.method = "first") # get the index of the first maximum
idx <- replace(idx, rowSums(o) == 0, NA) # take care of cases without greater Value
db$Resp <- db$Year[idx] # add new column
The resulting table is:
# Year Target Value Resp
# 1 2010 3 4 2011
# 2 2011 5 5 2013
# 3 2012 2 2 2013
# 4 2013 7 7 2015
# 5 2014 5 4 2015
# 6 2015 8 9 NA
# 7 2016 3 5 2017
# 8 2017 6 8 NA