Create new column with binary data or presence/absence data in R [duplicate]

Answer 1

Use ifelse:

> df <- data.frame(Species_code = c(101, 103,101,99,101)) # your data
> df$Presence_absence <- ifelse(df$Species_code==101, 1, 0) # this does the trick
> df
  Species_code Presence_absence
1          101                1
2          103                0
3          101                1
4           99                0
5          101                1