rmse_by_num_trees {bartMachine} R Documentation

## Assess the Out-of-sample RMSE by Number of Trees

### Description

Assess out-of-sample RMSE of a BART model for varying numbers of trees in the sum-of-trees model.

### Usage

```rmse_by_num_trees(bart_machine, tree_list = c(5, seq(10, 50, 10), 100, 150, 200),
in_sample = FALSE, plot = TRUE, holdout_pctg = 0.3, num_replicates = 4, ...)
```

### Arguments

 `bart_machine` An object of class “bartMachine”. `tree_list` List of sizes for the sum-of-trees models. `in_sample` If TRUE, the RMSE is computed on in-sample data rather than an out-of-sample holdout. `plot` If TRUE, a plot of the RMSE by the number of trees in the ensemble is created. `holdout_pctg` Percentage of the data to be treated as an out-of-sample holdout. `num_replicates` Number of replicates to average the results over. Each replicate uses a randomly sampled holdout of the data, (which could have overlap). `...` Other arguments to be passed to the plot function.

### Value

Invisibly, returns the out-of-sample average RMSEs for each tree size.

### Note

Since using a large number of trees can substantially increase computation time, this plot can help assess whether a smaller ensemble size is sufficient to obtain desirable predictive performance. This function is parallelized by the number of cores set in `set_bart_machine_num_cores`.

### Examples

```## Not run:
#generate Friedman data
set.seed(11)
n  = 200
p = 10
X = data.frame(matrix(runif(n * p), ncol = p))
y = 10 * sin(pi* X[ ,1] * X[,2]) +20 * (X[,3] -.5)^2 + 10 * X[ ,4] + 5 * X[,5] + rnorm(n)

##build BART regression model
bart_machine = bartMachine(X, y, num_trees = 20)

#explore RMSE by number of trees
rmse_by_num_trees(bart_machine)

## End(Not run)

```

[Package bartMachine version 1.2.6 Index]