R: Fast Random Forests

rfsrc.fast {randomForestSRC} | R Documentation

## Fast Random Forests

### Description

Fast approximate random forests using subsampling with forest options set to encourage computational speed. Applies to all families.

### Usage

    rfsrc.fast(formula, data,
      ntree = 500,
      nsplit = 10,
      bootstrap = "by.root",
      ensemble = "oob",
      sampsize = function(x){min(x * .632, max(150, x ^ (3/4)))},
      samptype = "swor",
      samp = NULL,
      ntime = 50,
      forest = FALSE,
      terminal.qualts = FALSE,
      ...)

### Arguments

`formula` | A symbolic description of the model to be fit. If missing, unsupervised splitting is implemented.
`data` | Data frame containing the y-outcome and x-variables.
`ntree` | Number of trees.
`nsplit` | Non-negative integer value specifying number of random split points used to split a node (deterministic splitting corresponds to the value zero and is much slower).
`bootstrap` | Bootstrap protocol used in growing a tree.
`ensemble` | Specifies the type of ensemble. We request only out-of-sample which corresponds to "oob".
`sampsize` | Function specifying size of subsampled data. Can also be a number.
`samptype` | Type of bootstrap used.
`samp` | Bootstrap specification when `"by.user"` is used.
`ntime` | Integer value used for survival to constrain ensemble calculations to a grid of `ntime` time points.
`forest` | Should the forest object be returned? Turn this on if you want prediction on test data but for big data this can be large.
`terminal.qualts` | Should terminal node membership information be returned? Ensure this is off in the presence of big data as memory warnings can occur otherwise. In either case, this parameter does not effect the ability to restore the model. When this is `FALSE`, the training data must be sent down the tree when restoring the model. When this is `TRUE`, terminal node membership is assigned based on the contents of this output during model restoration, resulting in a faster CPU times.
`...` | Further arguments to be passed to `rfsrc`.

### Details

Calls `rfsrc` under various options (including subsampling) to encourage computational speeds. This will provide a good approximation but will not be as good as default settings of `rfsrc`.

### Value

An object of class `(rfsrc, grow)`.

### Author(s)

Hemant Ishwaran and Udaya B. Kogalur

### See Also

`rfsrc`

### Examples

    ## ------------------------------------------------------------
    ## Iowa housing regression example
    ## ------------------------------------------------------------

    ## load the Iowa housing data
    data(housing, package = "randomForestSRC")

    ## do quick and *dirty* imputation
    housing <- impute(SalePrice ~ ., housing,
             ntree = 50, nimpute = 1, splitrule = "random")

    ## grow a fast forest
    o1 <- rfsrc.fast(SalePrice ~ ., housing)
    o2 <- rfsrc.fast(SalePrice ~ ., housing, nodesize = 1)
    print(o1)
    print(o2)

    ## grow a fast bivariate forest
    o3 <- rfsrc.fast(cbind(SalePrice,Overall.Qual) ~ ., housing)
    print(o3)

    ## ------------------------------------------------------------
    ## White wine classification example
    ## ------------------------------------------------------------

    data(wine, package = "randomForestSRC")
    wine$quality <- factor(wine$quality)
    o <- rfsrc.fast(quality ~ ., wine)
    print(o)

    ## ------------------------------------------------------------
    ## pbc survival example
    ## ------------------------------------------------------------

    data(pbc, package = "randomForestSRC")
    o <- rfsrc.fast(Surv(days, status) ~ ., pbc)
    print(o)

    ## ------------------------------------------------------------
    ## WIHS competing risk example
    ## ------------------------------------------------------------

    data(wihs, package = "randomForestSRC")
    o <- rfsrc.fast(Surv(time, status) ~ ., wihs)
    print(o)

[Package randomForestSRC version 2.9.3 Index]