2.2 嗜好の収集（p10）

Lisa.Rose        <- c(2.5, 3.5, 3.0, 3.5, 2.5, 3.0)
Gene.Seymour     <- c(3.0, 3.5, 1.5, 5.0, 3.5, 3.0)
Michael.Phillips <- c(2.5, 3.0, NA, 3.5, NA, 4.0)
Claudia.Puig     <- c(NA, 3.5, 3.0, 4.0, 2.5, 4.5)
Mick.LaSalle     <- c(3.0, 4.0, 2.0, 3.0, 2.0, 3.0)
Jack.Matthews    <- c(3.0, 4.0, NA, 5.0, 3.5, 3.0)
Toby             <- c(NA, 4.5, NA, 4.0, 1.0, NA)
critics          <- cbind(Lisa.Rose, Gene.Seymour, Michael.Phillips, Claudia.Puig,
                          Mick.LaSalle, Jack.Matthews, Toby)
rownames(critics)<- c("Lady.in.the.Water", "Snakes.on.a.Plane", "Just.My.Luck",
                      "Superman.Returns", "You.Me.and.Dupree", "The.Night.Listener")
critics
#                    Lisa.Rose Gene.Seymour Michael.Phillips Claudia.Puig Mick.LaSalle Jack.Matthews Toby
# Lady.in.the.Water        2.5          3.0              2.5           NA            3           3.0   NA
# Snakes.on.a.Plane        3.5          3.5              3.0          3.5            4           4.0  4.5
# Just.My.Luck             3.0          1.5               NA          3.0            2            NA   NA
# Superman.Returns         3.5          5.0              3.5          4.0            3           5.0  4.0
# You.Me.and.Dupree        2.5          3.5               NA          2.5            2           3.5  1.0
# The.Night.Listener       3.0          3.0              4.0          4.5            3           3.0   NA

critics[,"Toby"]
# Lady.in.the.Water  Snakes.on.a.Plane       Just.My.Luck   Superman.Returns  You.Me.and.Dupree The.Night.Listener 
#                NA                4.5                 NA                4.0                1.0                 NA 

# NAが混ざるのがいやなら
temp <- na.omit(critics[,"Toby"])
temp[1:length(temp)]
# Snakes.on.a.Plane  Superman.Returns You.Me.and.Dupree 
#              4.5               4.0               1.0