2.1.2. patsy.builtins.I¶

patsy.builtins.I(x)[source]¶

The identity function. Simply returns its input unchanged.

Since Patsy’s formula parser ignores anything inside a function call syntax, this is useful to ‘hide’ arithmetic operations from it. For instance:

y ~ x1 + x2

has x1 and x2 as two separate predictors. But in:

y ~ I(x1 + x2)

we instead have a single predictor, defined to be the sum of x1 and x2.