R中另一列因子的标记因子

Question

I have a dtaframe with a column/vector of 2 factor levels...these can change, but there will always be 2 of them. I want to create a new column/vector that assigns a '0' for the first factor and a '1' for the second.....so no matter what my original factor field is i always get a column of zeros and ones.

PART   col1    newcol
 A      a       0
 A      a       0
 A      a       0
 A      a       0
 A      b       1
 A      b       1
 A      b       1
 A      b       1
 B      c       0
 B      c       0
 B      c       0
 B      c       0
 B      d       1
 B      d       1
 B      d       1
 B      d       1

But col1 one could be b or c, or d or e...etc....either way I just always want to create the col with the '0' & '1'. It should be grouped by the first 'PART' column.

Hope this makes sense... Paul.

Answer 1

You can try

library(dplyr)
df1 %>% 
    group_by(PART) %>%    
    mutate(newcol=factor(col1, labels=0:1))
    #or
    #mutate(newcol= as.numeric(factor(col1))-1)
#    PART col1 newcol
#1     A    a      0
#2     A    a      0
#3     A    a      0
#4     A    a      0
#5     A    b      1
#6     A    b      1
#7     A    b      1
#8     A    b      1
#9     B    c      0
#10    B    c      0
#11    B    c      0
#12    B    c      0
#13    B    d      1
#14    B    d      1
#15    B    d      1
#16    B    d      1

Or using ave from base R

 with(df1, as.numeric(ave(as.character(col1), PART, FUN=factor)))-1
 #[1] 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1