mape.md

mape	R Documentation

Mean Absolute Percentage Error

Description

A generic S3 function to compute the mean absolute percentage error score for a regression model. This function dispatches to S3 methods inmape() and performs no input validation. If you supply NA values or vectors of unequal length (e.g. length(x) != length(y)), the underlying C++ code may trigger undefined behavior and crash your R session.

Defensive measures

Because mape() operates on raw pointers, pointer-level faults (e.g. from NA or mismatched length) occur before any R-level error handling. Wrapping calls in try() or tryCatch() will not prevent R-session crashes.

To guard against this, wrap mape() in a "safe" validator that checks for NA values and matching length, for example:

safe_mape <- function(x, y, ...) {
  stopifnot(
    !anyNA(x), !anyNA(y),
    length(x) == length(y)
  )
  mape(x, y, ...)
}

Apply the same pattern to any custom metric functions to ensure input sanity before calling the underlying C++ code.

Usage

## Generic S3 method
## for Mean Absolute Percentage Error
mape(...)

## Generic S3 method
## for weighted Mean Absolute Percentage Error
weighted.mape(...)

Arguments

...	Arguments passed on to mape.numeric,weighted.mape.numeric actual,predicted A pair of <double> vectors of length n. w A <double> vector of sample weights.

Value

A <double> value

References

James, Gareth, et al. An introduction to statistical learning. Vol. 112. No. 1. New York: springer, 2013.

Hastie, Trevor. "The elements of statistical learning: data mining, inference, and prediction." (2009).

Virtanen, Pauli, et al. "SciPy 1.0: fundamental algorithms for scientific computing in Python." Nature methods 17.3 (2020): 261-272.

Examples

## Generate actual
## and predicted values
actual_values    <- c(1.3, 0.4, 1.2, 1.4, 1.9, 1.0, 1.2)
predicted_values <- c(0.7, 0.5, 1.1, 1.2, 1.8, 1.1, 0.2)

## Evaluate performance
SLmetrics::mape(
   actual    = actual_values, 
   predicted = predicted_values
)

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