Imagine stations on several train lines. Given a station pair, find the lines that allow travel between these stations (no transfers!)
> # install.packages("qpcR")
> library(qpcR)
> stations = qpcR:::cbind.na(EWL=c("Pasir Ris", "Tampines", "Simei", "Tanah Merah", "Bedok", "Kembangan", "Eunos", "Paya Lebar", "Aljunied", "Kallang", "Lavender", "Bugis", "City Hall", "Raffles Place", "Tanjong Pagar", "Outram Park", "Tiong Bahru", "Redhill", "Queenstown", "Commonwealth", "Buona Vista", "Dover", "Clementi", "Jurong East", "Chinese Garden", "Lakeside", "Boon Lay", "Pioneer", "Joo Koon"),
+ NSL=c("Jurong East", "Bukit Batok", "Bukit Gombak", "Choa Chu Kang", "Yew Tee", "Kranji", "Marsiling", "Woodlands", "Admiralty", "Sembawang", "Canberra", "Yishun", "Khatib", "Yio Chu Kang", "Ang Mo Kio", "Bishan", "Braddell", "Toa Payoh", "Novena", "Newton", "Orchard", "Somerset", "Dhoby Ghaut", "City Hall", "Raffles Place", "Marina Bay", "Marina South Pier"),
+ NEL=c("HarbourFront", "Outram Park", "Chinatown", "Clarke Quay", "Dhoby Ghaut", "Little India", "Farrer Park", "Boon Keng", "Potong Pasir", "Woodleigh", "Serangoon", "Kovan", "Hougang", "Buangkok", "Sengkang", "Punggol"),
+ CCL=c("Dhoby Ghaut", "Bras Basah", "Esplanade", "Promenade", "Nicoll Highway", "Stadium", "Mountbatten", "Dakota", "Paya Lebar", "MacPherson", "Tai Seng", "Bartley", "Serangoon", "Lorong Chuan", "Bishan", "Marymount", "Caldecott", "Bukit Brown", "Botanic Gardens", "Farrer Road", "Holland Village", "Buona Vista", "one-north", "Kent Ridge", "Haw Par Villa", "Pasir Panjang", "Labrador Park", "Telok Blangah", "HarbourFront"),
+ DTL=c("Bukit Panjang", "Cashew", "Hillview", "Beauty World", "King Albert Park", "Sixth Avenue", "Tan Kah Kee", "Botanic Gardens", "Stevens", "Newton", "Little India", "Rochor", "Bugis", "Promenade", "Bayfront", "Downtown", "Telok Ayer", "Chinatown"))
> apply(stations, 2, function(route) { all(c("Dhoby Ghaut", "Bishan") %in% route) })
EWL NSL NEL CCL DTL
FALSE TRUE FALSE TRUE FALSE