Description Usage Arguments Details Value Author(s) See Also Examples

View source: R/dropEmptyLevels.R

Reform a factor so that only necessary levels are kept.

1 |

`x` |
a factor or a vector to be converted to a factor. |

In general, the levels of a factor, `levels(x)`

, may include values that never actually occur.
This function drops any levels of that do not occur.

If `x`

is not a factor, then the function returns `factor(x)`

.
If `x`

is a factor, then the function returns the same value as `factor(x)`

or `x[,drop=TRUE]`

but somewhat more efficiently.

A factor with the same values as `x`

but with a possibly reduced set of levels.

Gordon Smyth

1 2 3 | ```
x <- factor(c("a","b"), levels=c("c","b","a"))
x
dropEmptyLevels(x)
``` |

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