Factor
- Create
- Get
- Update
Create
| What | How | Details |
| From vector | factor(x) | |
| From vector, with renamed levels | factor(x, levels=1:3, labels=LETTERS[1:3]) | |
| Generate by pattern | gl(5, 2, labels=LETTERS[1:5]) | |
| Generate factor of interactions with another | interaction(f1, f2) | |
| Combine factors | factor(c(as.character(x), as.character(y)), union(levels(x), levels(y))) | |
Get
| What | How | Details |
| Levels | levels(f) | |
| Number of levels | nlevels(f) | |
| Subset and drop unused levels | f[1:2, drop=TRUE] | |
Update
| What | How | Details |
| Add NA as a factor level | addNA(f) | |
Add NA as a factor level in data.table | dt[is.na(f), f := 'NA'] | |
| Drop unused factors levels | factor(f) | |
| Drop factor levels | droplevels(f, exclude=X) | |
| Drop factor levels except for | droplevels(f, except=X) | |
| Remap factor | x = factor(c('a1', 'b1', 'a2', 'c1'))
factor(x, levels=levels(x), labels=c('a', 'a', 'b', 'c')) | |