library(tidyverse)
(mydata <- data.frame(
cd1=c(1,3),
cp1=c("a","c"),
cd2=c(2,4),
cp2=c("b","d")
))
(first <- mydata %>% select(date=cd1,place=cp1) %>% mutate(rn=row_number()))
(second <- mydata %>% select(date=cd2,place=cp2)%>% mutate(rn=row_number()))
(fin <- bind_rows(first,second) %>% arrange(rn))