Model predictions

Apply to a model to create different types of predictions. predict() can be used for all types of models and uses the "type" argument for more specificity.

Usage

# S3 method for cluster_fit
predict(object, new_data, type = NULL, opts = list(), ...)

# S3 method for cluster_fit
predict_raw(object, new_data, opts = list(), ...)

Arguments

object: An object of class cluster_fit.
new_data: A rectangular data object, such as a data frame.
type: A single character value or NULL. Possible values are "cluster", or "raw". When NULL, predict() will choose an appropriate value based on the model's mode.
opts: A list of optional arguments to the underlying predict function that will be used when type = "raw". The list should not include options for the model object or the new data being predicted.
...: Arguments to the underlying model's prediction function cannot be passed here (see opts).

Value

With the exception of type = "raw", the results of predict.cluster_fit() will be a tibble as many rows in the output as there are rows in new_data and the column names will be predictable.

For clustering results the tibble will have a .pred_cluster column.

Using type = "raw" with predict.cluster_fit() will return the unadulterated results of the prediction function.

When the model fit failed and the error was captured, the predict()

function will return the same structure as above but filled with missing values. This does not currently work for multivariate models.

Details

If "type" is not supplied to predict(), then a choice is made:

type = "cluster" for clustering models

predict() is designed to provide a tidy result (see "Value" section below) in a tibble output format.

The ordering of the clusters is such that the first observation in the training data set will be in cluster 1, the next observation that doesn't belong to cluster 1 will be in cluster 2, and so on and forth. As the ordering of clustering doesn't matter, this is done to avoid identical sets of clustering having different labels if fit multiple times.

What does it mean to predict?

Prediction is not always formally defined for clustering models. Therefore, each cluster_spec method will have their own section on how "prediction" is interpreted, and done if implemented.

predict() when used with tidyclust objects is a part of a trio of functions doing similar things:

extract_cluster_assignment() returns the cluster assignments of the training observations
extract_centroids() returns the location of the centroids
predict() returns the cluster a new observation belongs to

Examples

kmeans_spec <- k_means(num_clusters = 5) %>%
  set_engine("stats")

kmeans_fit <- fit(kmeans_spec, ~., mtcars)

kmeans_fit %>%
  predict(new_data = mtcars)
#> # A tibble: 32 × 1
#>    .pred_cluster
#>    <fct>        
#>  1 Cluster_1    
#>  2 Cluster_1    
#>  3 Cluster_2    
#>  4 Cluster_3    
#>  5 Cluster_4    
#>  6 Cluster_1    
#>  7 Cluster_4    
#>  8 Cluster_2    
#>  9 Cluster_2    
#> 10 Cluster_1    
#> # ℹ 22 more rows

# Some models such as `hier_clust()` fits in such a way that you can specify
# the number of clusters after the model is fit
hclust_spec <- hier_clust() %>%
  set_engine("stats")

hclust_fit <- fit(hclust_spec, ~., mtcars)

hclust_fit %>%
  predict(new_data = mtcars[4:6, ], num_clusters = 2)
#> # A tibble: 3 × 1
#>   .pred_cluster
#>   <fct>        
#> 1 Cluster_1    
#> 2 Cluster_2    
#> 3 Cluster_1    

hclust_fit %>%
  predict(new_data = mtcars[4:6, ], cut_height = 250)
#> # A tibble: 3 × 1
#>   .pred_cluster
#>   <fct>        
#> 1 Cluster_2    
#> 2 Cluster_2    
#> 3 Cluster_2