# Factors in Stata and R

The quick version of this post goes like this:

-- # in Stata is : in R

-- ## in Stata is * in R.

The long version is that both Stata and R handle very nicely factor variables in regression models. If you want a full-factorial interaction between a factor variable x1 and a continuous variable x2, the Stata way is to say

```
regress y i.x1##c.x2
```

whereas the R way is to say

```
lm(y~factor(x1)*x2)
```

Now, if you just want to interact x1 with the slope of x2, the Stata way becomes

```
regress y i.x1#c.x2
```

whereas the R way becomes

```
lm(y~factor(x1):x2)
```

That's all.