`num2char` represents a column number as its corresponding generator.
num2char(x)
| x | Number of the interaction |
|---|
A character of length larger or equal to one, corresponding to a generator. For any number n, the length of the character will always be ceil(log2(n)).
Column number are always positive, non-zero integers. Basic factors are power of two, while added factors are decomposed in powers of two and their corresponding generator is build from it. A generator corresponds to the basic factors used to create the levels of the added factor. All basic factors are represented by independent lowercase letters.
num2char(4)#> [1] "c"num2char(13)#> [1] "acd"