bugfix prediction_glm.R newdata argument

[vincentarelbundock]

This is a minor bugfix (with a new test) for: https://github.com/leeper/prediction/issues/32

I'm not sure how your version numbers work, so I just added a new entry to NEWS.

library(prediction)
data(mtcars)

# `data` with lm works
mod <- lm(am ~ hp + drat, data = mtcars)
prediction(mod, data = data.frame(hp = 110, drat = 3.9))
#> Data frame with 1 predictions from
#>  lm(formula = am ~ hp + drat, data = mtcars)
#> with average prediction: 0.5947

# `data` with glm doesn't work
mod <- glm(am ~ hp + drat, data = mtcars)
prediction(mod, data = data.frame(hp = 110, drat = 3.9))
#> Warning in model$family$mu.eta(predictions_link) * model_mat: longer object
#> length is not a multiple of shorter object length
#> Error in is.data.frame(x): dims [product 3] do not match the length of object [32]

This problem was caused by calling predict(data = ) instead of predict(newdata = in a couple places in prediction_glm.R.

Please ensure the following before submitting a PR:

• [x] if suggesting code changes or improvements, open an issue first
• [x] for all but trivial changes (e.g., typo fixes), add your name to DESCRIPTION
• [x] for all but trivial changes (e.g., typo fixes), documentation your change in NEWS.md with a parenthetical reference to the issue number being addressed
• [x] if changing documentation, edit files in /R not /man and run devtools::document() to update documentation
• [x] add code or new test files to /tests for any new functionality or bug fix
• [x] make sure R CMD check runs without error before submitting the PR

[vincentarelbundock]

@leeper When you have a second, do you think you could take a look at this one? This PR would allow me to fix Travis failures and finish up work downstream in margins for my ggplot WIP PR.

I only modified 2 lines of actual code and added a test, so it shouldn't be very difficult to review. I also added my name as contributor, but this is so minor that I would be happy to remove it.

Travis works in 5 of the 6 cases; the only case where it fails relates to package installation in an old R release, so it has nothing to do with this commit.

[leeper]

Looks great. Thanks!

[vincentarelbundock]

Thanks!