Use the colClasses
argument to read.csv
.
Data <- read.csv(text="Lower.Zip, Upper.Zip, Zone
004, 005, Zone.8
006, 007, Zone.45
009, , Zone.45
010, 089, Zone.8
100, 339, Zone.8",
colClasses=rep("character",3)) # you may want to add strip.white=TRUE