# predict.train

##### Extract predictions and class probabilities from train objects

These functions can be used for a single `train`

object or to loop through a number of `train`

objects to calculate the
training and test data predictions and class probabilities.

- Keywords
- manip

##### Usage

```
## S3 method for class 'list':
predict(object, ...)
```## S3 method for class 'train':
predict(object, newdata = NULL, type = "raw", ...)

extractPrediction(models,
testX = NULL, testY = NULL,
unkX = NULL,
unkOnly = !is.null(unkX) & is.null(testX),
verbose = FALSE)

extractProb(models,
testX = NULL, testY = NULL,
unkX = NULL,
unkOnly = !is.null(unkX) & is.null(testX),
verbose = FALSE)

##### Arguments

- object
- For
`predict.train`

, an object of class`train`

. For`predict.list`

, a list of objects of class`train`

. - newdata
- an optional set of data to predict on. If
`NULL`

, then the original training data are used - type
- either "raw" or "prob", for the number/class predictions or class probabilities, respectively. Class probabilities are not available for all classification models
- models
- a list of objects of the class
`train`

. The objects must have been generated with`fitBest = FALSE`

and`returnData = TRUE`

. - testX
- an optional set of data to predict
- testY
- an optional outcome corresponding to the data given in
`testX`

- unkX
- another optional set of data to predict without known outcomes
- unkOnly
- a logical to bypass training and test set predictions. This is useful if speed is needed for unknown samples.
- verbose
- a logical for printing messages
- ...
- additional arguments to be passed to other methods

##### Details

These functions are wrappers for the specific prediction functions in each modeling package. In each case, the optimal tuning values given in the `tuneValue`

slot of the `finalModel`

object are used to predict.

To get simple predictions for a new data set, the `predict`

function can be used. Limits can be imposed on the range of predictions. See `trainControl`

for more information.

To get predictions for a series of models at once, a list of `train`

objects can be passes to the `predict`

function and a list of model predictions will be returned.

The two extraction functions can be used to get the predictions and observed outcomes at once for the training, test and/or unknown samples at once in a single data frame (instead of a list of just the predictions). These objects can then be passes to `plotObsVsPred`

or `plotClassProbs`

.

##### Value

- For
`predict.train`

, a vector of predictions if`type = "raw"`

or a data frame of class probabilities for`type = "probs"`

. In the latter case, there are columns for each class.For

`predict.list`

, a list results. Each element is produced by`predict.train`

.For

`extractPrediction`

, a data frame with columns: obs the observed training and test data pred predicted values model the type of model used to predict object the names of the objects within `models`

. If`models`

is an un-named list, the values of`object`

will be "Object1", "Object2" and so ondataType "Training", "Test" or "Unknown" depending on what was specified - For
`extractProb`

, a data frame. There is a column for each class containing the probabilities. The remaining columns are the same as above (although the`pred`

column is the predicted class)

##### References

Kuhn (2008), ``Building Predictive Models in R Using the caret'' (

##### See Also

##### Examples

```
library(mlbench)
data(Satellite)
numSamples <- dim(Satellite)[1]
set.seed(716)
varIndex <- 1:numSamples
trainSamples <- sample(varIndex, 150)
varIndex <- (1:numSamples)[-trainSamples]
testSamples <- sample(varIndex, 100)
varIndex <- (1:numSamples)[-c(testSamples, trainSamples)]
unkSamples <- sample(varIndex, 50)
trainX <- Satellite[trainSamples, -37]
trainY <- Satellite[trainSamples, 37]
testX <- Satellite[testSamples, -37]
testY <- Satellite[testSamples, 37]
unkX <- Satellite[unkSamples, -37]
knnFit <- train(trainX, trainY, "knn")
rpartFit <- train(trainX, trainY, "rpart")
predict(knnFit)
predict(knnFit, newdata = testX)
predict(knnFit, type = "prob")
bothModels <- list(
knn = knnFit,
tree = rpartFit)
predict(bothModels)
predTargets <- extractPrediction(
bothModels,
testX = testX,
testY = testY,
unkX = unkX)
```

*Documentation reproduced from package caret, version 4.87, License: GPL-2*