augment() for models without class probabilities

[juliasilge]

Closes #435

This PR adds a tryCatch() for making the type = "prob" predictions in augment(), so that it only returns the class predictions if the class probability predictions fail:

library(parsnip)

svm_spec <- svm_linear() %>%
  set_mode("classification") %>%
  set_engine("LiblineaR")

svm_fit <- fit(svm_spec, Species ~ ., data = iris)

augment(svm_fit, iris)
#> # A tibble: 150 x 6
#>    Sepal.Length Sepal.Width Petal.Length Petal.Width Species .pred_class
#>           <dbl>       <dbl>        <dbl>       <dbl> <fct>   <fct>      
#>  1          5.1         3.5          1.4         0.2 setosa  setosa     
#>  2          4.9         3            1.4         0.2 setosa  setosa     
#>  3          4.7         3.2          1.3         0.2 setosa  setosa     
#>  4          4.6         3.1          1.5         0.2 setosa  setosa     
#>  5          5           3.6          1.4         0.2 setosa  setosa     
#>  6          5.4         3.9          1.7         0.4 setosa  setosa     
#>  7          4.6         3.4          1.4         0.3 setosa  setosa     
#>  8          5           3.4          1.5         0.2 setosa  setosa     
#>  9          4.4         2.9          1.4         0.2 setosa  setosa     
#> 10          4.9         3.1          1.5         0.1 setosa  setosa     
#> # … with 140 more rows

data(two_class_dat, package = "modeldata")

cls_form <-
  logistic_reg() %>%
  set_engine("glm") %>%
  fit(Class ~ ., data = two_class_dat)

augment(cls_form, two_class_dat)
#> # A tibble: 791 x 6
#>        A     B Class  .pred_class .pred_Class1 .pred_Class2
#>    <dbl> <dbl> <fct>  <fct>              <dbl>        <dbl>
#>  1  2.07 1.63  Class1 Class1             0.513      0.487  
#>  2  2.02 1.04  Class1 Class1             0.906      0.0940 
#>  3  1.69 1.37  Class2 Class1             0.645      0.355  
#>  4  3.43 1.98  Class2 Class1             0.599      0.401  
#>  5  2.88 1.98  Class1 Class2             0.435      0.565  
#>  6  3.31 2.41  Class2 Class2             0.201      0.799  
#>  7  2.50 1.56  Class2 Class1             0.701      0.299  
#>  8  1.98 1.55  Class2 Class1             0.563      0.437  
#>  9  2.88 0.580 Class1 Class1             0.994      0.00622
#> 10  3.74 2.74  Class2 Class2             0.105      0.895  
#> # … with 781 more rows

^{Created on 2021-05-11 by the reprex package (v2.0.0)}

[juliasilge]

This new change ⬆️ will fail until #489 is merged in.

[github-actions]

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