Add a substring based on a condition in r

Question

I would like to add a substring add the end of a string variable in my data. This variable represents a question asked during a specific case and can be either irrelevant ("00"), partially relevant ("01") or very relevant ("02"). Hence I would like to make this a conditional statement based on the specific value of the case ID. Here is some sample data:

Case_ID	Question
1234	QS1
4321	QS1
1234	QS3
1234	QS2
4321	QS3
4321	QS2

Where: Case_ID 1234: QS1 very relevant ("02") , QS2 irrelevant ("00"), QS3 irrelevant ("00) AND Case_ID 4321: QS1 irrelevant ("00"), QS2 partially relevant ("01"), QS3 very relevant ("02).

I hope to receive the following output:

Case_ID	Question
1234	QS102
4321	QS100
1234	QS300
1234	QS200
4321	QS302
4321	QS201

Answer 1

You can do a very 'by hand' solution with if statements

df = tibble(
  Case_ID = c(1234, 4321,    1234,  1234,    4321,  4321),
  Question = c("QS1", "QS1", "QS3", "QS2", "QS3", "QS2"))

relevance = function(case, question) {
  if(case == 1234) {
    if(question == "QS1") {"02"}
    else {"00"}}
  else {
    if(question == "QS1") {"00"}
    else if(question == "QS2") {"01"}
    else {"02"}}}

df %>%
  rowwise() %>%
  mutate(Question = paste0(Question, relevance(Case_ID, Question)))

# A tibble: 6 x 2
# Rowwise: 
  Case_ID Question
    <dbl> <chr>   
1    1234 QS102   
2    4321 QS100   
3    1234 QS300   
4    1234 QS200   
5    4321 QS302   
6    4321 QS201