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rglm

How to fit polynomial model of all predictors using "." in R?

I'm trying to fit a logistic regression model using all predictors as a polynomial model. I've tried doing this but didn't work:

poly_model = glm(type~ poly(., 2), data=train_data, family=binomial)

I'm using the built in dataset:

train_data = MASS::Pima.tr

What's the correct way to do this?

Solution

  • There's not really a way to do that with the . syntax. You'll need to explictly build the formula yourself. You can do this with a helper function

    get_formula <- function(resp) {
  reformulate(
    sapply(setdiff(names(train_data), resp), function(x) paste0("poly(", x, ", 2)")),
    response = resp
  )
}


model <- get_formula("type")
model
# type ~ poly(npreg, 2) + poly(glu, 2) + poly(bp, 2) + poly(skin, 
#     2) + poly(bmi, 2) + poly(ped, 2) + poly(age, 2)
glm(model, data=train_data, family=binomial)