nullmodel  R Documentation 
Fit a single mean or largest class model. nullmodel()
is the underlying
computational function for the null_model()
specification.
nullmodel(x, ...)
## Default S3 method:
nullmodel(x = NULL, y, ...)
## S3 method for class 'nullmodel'
print(x, ...)
## S3 method for class 'nullmodel'
predict(object, new_data = NULL, type = NULL, ...)
x 
An optional matrix or data frame of predictors. These values are not used in the model fit 
... 
Optional arguments (not yet used) 
y 
A numeric vector (for regression) or factor (for classification) of outcomes 
object 
An object of class 
new_data 
A matrix or data frame of predictors (only used to determine the number of predictions to return) 
type 
Either "raw" (for regression), "class" or "prob" (for classification) 
nullmodel()
emulates other model building functions, but returns the
simplest model possible given a training set: a single mean for numeric
outcomes and the most prevalent class for factor outcomes. When class
probabilities are requested, the percentage of the training set samples with
the most prevalent class is returned.
The output of nullmodel()
is a list of class nullmodel
with elements
call 
the function call 
value 
the mean of

levels 
when 
pct 
when 
n

the number of elements in 
predict.nullmodel()
returns either a factor or numeric vector
depending on the class of y
. All predictions are always the same.
outcome < factor(sample(letters[1:2],
size = 100,
prob = c(.1, .9),
replace = TRUE))
useless < nullmodel(y = outcome)
useless
predict(useless, matrix(NA, nrow = 5))
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