boot {CarletonStats} R Documentation

## Bootstrap

### Description

Bootstrap a single variable or a grouped variable

### Usage

```boot(x, ...)

## Default S3 method:
boot(x, group = NULL, statistic = mean,
conf.level = 0.95, B = 10000, plot.hist = TRUE,
legend.loc = "topright", plot.qq = FALSE,
x.name = deparse(substitute(x)), ...)

## S3 method for class 'formula'
boot(formula, data, subset, ...)
```

### Arguments

 `x` a numeric vector `...` further arguments to be passed to or from methods. `group` an optional grouping variable (vector), usually a factor variable. If it is a binary numeric variable, it will be coerced to a factor. `statistic` function that computes the statistic of interest. Default is the `mean`. `conf.level` confidence level for the bootstrap percentile interval. Default is 95%. `B` number of times to resample (positive integer greater than 2). `plot.hist` logical value. If `TRUE`, plot the histogrom of the bootstrap distribution. `legend.loc` where to place the legend on the histogram. Default is `"topright"`. Other options include `"topleft"`, `"bottomleft"` and `"bottomright"`. `plot.qq` Logical value. If `TRUE`, create a normal quantile-quantile plot of the bootstrap distribution. `x.name` Label for variable name `formula` a formula `y ~ g` where `y` is a numeric vector and `g` a factor variable with two levels. If `g` is a binary numeric vector, it will be coerced to a factor variable. For a single numeric variable, formula may also be `~ y`. `data` a data frame that contains the variables given in the formula. `subset` an optional expression indicating what observations to use.

### Details

Perform a bootstrap of a statistic applied to a single variable, or to the difference of the statistic computed on two samples (using the grouping variable). If `x` is a binary vector of 0's and 1's and the function is the mean, then the statistic of interest is the proportion.

Observations with missing values are removed.

### Value

A vector with the resampled statistics is returned invisibly.

### Methods (by class)

• `default`: Bootstrap a single variable or a grouped variable

• `formula`: Bootstrap a single variable or a grouped variable

Laura Chihara

### References

Tim Hesterberg's website http://www.timhesterberg.net/bootstrap

### Examples

```
#ToothGrowth data (supplied by R)
#bootstrap mean of a single numeric variable
boot(ToothGrowth\$len)

#bootstrap difference in mean of tooth length for two groups.
boot(ToothGrowth\$len, ToothGrowth\$supp)

#same as above using formula syntax
boot(len ~ supp, data = ToothGrowth)

```

[Package CarletonStats version 2.0 Index]