/usr/lib/R/site-library/checkmate/doc/checkmate.Rmd is in r-cran-checkmate 1.6.0-1.
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title: "Checkmate"
author: "Michel Lang"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
%\VignetteIndexEntry{Vignette Title}
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---
Ever used an R function that produced a not-very-helpful error message, just to discover after minutes of debugging that you simply passed a wrong argument?
Blaming the laziness of the package author for not doing such standard checks (in a dynamically typed language such as R) is at least partially unfair, as R makes theses types of checks cumbersome and annoying. Well, that's how it was in the past.
Enter checkmate.
Virtually **every standard type of user error** when passing arguments into function can be caught with a simple, readable line which produces an **informative error message** in case.
A substantial part of the package was written in C to **minimize any worries about execution time overhead**.
## Intro
As a motivational example, consider you have a function to calculate the faculty of a natural number and the user may choose between using either the stirling approximation or R's `factorial` function (which internally uses the gamma function).
Thus, you have two arguments, `n` and `method`.
Argument `n` must obviously be a positive natural number and `method` must be either `"stirling"` or `"factorial"`.
Here is a version of all the hoops you need to jump through to ensure that these simple requirements are met:
```{r}
fact <- function(n, method = "stirling") {
if (length(n) != 1)
stop("Argument 'n' must have length 1")
if (!is.numeric(n))
stop("Argument 'n' must be numeric")
if (is.na(n))
stop("Argument 'n' may not be NA")
if (is.double(n)) {
if (is.nan(n))
stop("Argument 'n' may not be NaN")
if (is.infinite(n))
stop("Argument 'n' must be finite")
if (abs(n - round(n, 0)) > sqrt(.Machine$double.eps))
stop("Argument 'n' must be an integerish value")
n <- as.integer(n)
}
if (n < 0)
stop("Argument 'n' must be >= 0")
if (length(method) != 1)
stop("Argument 'method' must have length 1")
if (!is.character(method) || !method %in% c("stirling", "factorial"))
stop("Argument 'method' must be either 'stirling' or 'factorial'")
if (method == "factorial")
factorial(n)
else
sqrt(2 * pi * n) * (n / exp(1))^n
}
```
And for comparison, here is the same function using checkmate:
```{r}
fact <- function(n, method = "stirling") {
library(checkmate)
assertCount(n)
assertChoice(method, c("stirling", "factorial"))
if (method == "factorial")
factorial(n)
else
sqrt(2 * pi * n) * (n / exp(1))^n
}
```
## Function overview
### Scalars
* [checkFlag](http://www.rdocumentation.org/packages/checkmate/functions/checkFlag)
* [checkCount](http://www.rdocumentation.org/packages/checkmate/functions/checkCount)
* [checkInt](http://www.rdocumentation.org/packages/checkmate/functions/checkInt)
* [checkNumber](http://www.rdocumentation.org/packages/checkmate/functions/checkNumber)
* [checkString](http://www.rdocumentation.org/packages/checkmate/functions/checkString)
* [checkScalar](http://www.rdocumentation.org/packages/checkmate/functions/checkScalar)
* [checkScalarNA](http://www.rdocumentation.org/packages/checkmate/functions/checkScalarNA)
* [checkPercentage](http://www.rdocumentation.org/packages/checkmate/functions/checkPercentage)
### Vectors
* [checkLogical](http://www.rdocumentation.org/packages/checkmate/functions/checkLogical)
* [checkNumeric](http://www.rdocumentation.org/packages/checkmate/functions/checkNumeric)
* [checkInteger](http://www.rdocumentation.org/packages/checkmate/functions/checkInteger)
* [checkIntegerish](http://www.rdocumentation.org/packages/checkmate/functions/checkIntegerish)
* [checkComplex](http://www.rdocumentation.org/packages/checkmate/functions/checkComplex)
* [checkCharacter](http://www.rdocumentation.org/packages/checkmate/functions/checkCharacter)
* [checkFactor](http://www.rdocumentation.org/packages/checkmate/functions/checkFactor)
* [checkList](http://www.rdocumentation.org/packages/checkmate/functions/checkList)
* [checkVector](http://www.rdocumentation.org/packages/checkmate/functions/checkVector)
* [checkAtomic](http://www.rdocumentation.org/packages/checkmate/functions/checkAtomic)
* [checkAtomicVector](http://www.rdocumentation.org/packages/checkmate/functions/checkAtomicVector)
### Attributes
* [checkClass](http://www.rdocumentation.org/packages/checkmate/functions/checkClass)
* [checkNames](http://www.rdocumentation.org/packages/checkmate/functions/checkNames)
* [checkNamed](http://www.rdocumentation.org/packages/checkmate/functions/checkNamed)
### Choices and Subsets
* [checkChoice](http://www.rdocumentation.org/packages/checkmate/functions/checkChoice)
* [checkSubset](http://www.rdocumentation.org/packages/checkmate/functions/checkSubset)
* [checkSetEqual](http://www.rdocumentation.org/packages/checkmate/functions/checkSetEqual)
### Matrices, Arrays and Data Frame
* [checkMatrix](http://www.rdocumentation.org/packages/checkmate/functions/checkMatrix)
* [checkArray](http://www.rdocumentation.org/packages/checkmate/functions/checkArray)
* [checkDataFrame](http://www.rdocumentation.org/packages/checkmate/functions/checkDataFrame)
### Safe Coercion to integer
* [asCount](http://www.rdocumentation.org/packages/checkmate/functions/asInteger)
* [asInt](http://www.rdocumentation.org/packages/checkmate/functions/asInteger)
* [asInteger](http://www.rdocumentation.org/packages/checkmate/functions/asInteger)
### Other builtin
* [checkNull](http://www.rdocumentation.org/packages/checkmate/functions/checkNull)
* [checkEnvironment](http://www.rdocumentation.org/packages/checkmate/functions/checkEnvironment)
* [checkFunction](http://www.rdocumentation.org/packages/checkmate/functions/checkFunction)
### File IO:
* [checkFile](http://www.rdocumentation.org/packages/checkmate/functions/checkFile)
* [checkDirectory](http://www.rdocumentation.org/packages/checkmate/functions/checkDirectory)
* [checkPathForOutput](http://www.rdocumentation.org/packages/checkmate/functions/checkPathForOutput)
## In case you miss flexibility
You can use [assert](http://www.rdocumentation.org/packages/checkmate/functions/assert) to perform multiple checks at once and throw an assertion if all checks fail.
## Argument Checks for the Lazy
The follwoing functions allow a special syntax to define argument checks using a special pattern.
E.g., `qassert(x, "I+")` asserts that `x` is an integer vector with at least one element and no missing values.
This provide a completely alternative mini-language (or style) how to perform argument checks.
You choose what you like best.
* [qassert](http://www.rdocumentation.org/packages/checkmate/functions/qassert)
* [qassertr](http://www.rdocumentation.org/packages/checkmate/functions/qassert)
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