using lm in list column to predict new values using purrr

Question

I am trying to add a column of predictions to a dataframe that has a list column that contains an lm model. I adopted some of the code from this post.

I have made a

Answer 1

You could take advantage of the newdata argument to predict.

I use map2_dbl so it returns just the single value rather than a list.

mutate(Pred = map2_dbl(model, 1:5, ~predict(.x, newdata = data.frame(ind = .y))))

# A tibble: 5 x 4
  groups         the_data    model       Pred
                      
1      A   -0.4822045
2      B   -0.1357712
3      C   -0.2455760
4      D    0.4818425
5      E   -0.3473236

If you add ind to the dataset before prediction you can use that column instead of 1:5.

mutate(ind = 1:5) %>%
    mutate(Pred = map2_dbl(model, ind, ~predict(.x, newdata = data.frame(ind = .y) )))

# A tibble: 5 x 5
  groups         the_data    model   ind       Pred
                       
1      A       1 -0.4822045
2      B       2 -0.1357712
3      C       3 -0.2455760
4      D       4  0.4818425
5      E       5 -0.3473236