testGeneric: Test for a generic summary statistic based on simulated data

In DHARMa: Residual Diagnostics for Hierarchical (Multi-Level / Mixed) Regression Models

Test for a generic summary statistic based on simulated data

Description

This function tests if a user-defined summary differs when applied to simulated / observed data.

Usage

testGeneric(simulationOutput, summary, alternative = c("two.sided",
  "greater", "less"), plot = T,
  methodName = "DHARMa generic simulation test")

Arguments

simulationOutput	an object of class DHARMa, either created via simulateResiduals for supported models or by createDHARMa for simulations created outside DHARMa, or a supported model. Providing a supported model directly is discouraged, because simulation settings cannot be changed in this case.
summary	a function that can be applied to simulated / observed data. See examples below
alternative	a character string specifying whether the test should test if observations are "greater", "less" or "two.sided" compared to the simulated null hypothesis
plot	whether to plot the simulated summary
methodName	name of the test (will be used in plot)

Details

This function applies a user-defined summary to the simulated/observed data of a DHARMa object and then performs a hypothesis test using the ratio Obs / Sim as the test statistic.

The summary is applied directly to the data and not to the residuals, but it can easily be remodeled to apply summaries to the residuals by simply defining something like f = function(x) summary (x - predictions), as done in testDispersion

Note

The summary function you specify will be applied to the data as it appears in your fitted model, which may not always be what you want.

As an example, consider the case where we want to test for n-inflation in k/n data. If you provide your data via cbind (k, n-k), you have to test for n-inflation, but if you provide your data via k/n and weights = n, you should test for 1-inflation. When in doubt, check how the data is represented internally in model.frame(model) or via simulate(model).

Author(s)

Florian Hartig

See Also

testResiduals, testUniformity, testOutliers, testDispersion, testZeroInflation, testGeneric, testTemporalAutocorrelation, testSpatialAutocorrelation, testQuantiles, testCategorical

Examples

testData = createData(sampleSize = 100, overdispersion = 0.5, randomEffectVariance = 0)
fittedModel <- glm(observedResponse ~ Environment1 , family = "poisson", data = testData)
simulationOutput <- simulateResiduals(fittedModel = fittedModel)

# the plot function shows 2 plots and runs 4 tests
# i) KS test i) Dispersion test iii) Outlier test iv) quantile test
plot(simulationOutput, quantreg = TRUE)

# testResiduals tests distribution, dispersion and outliers
testResiduals(simulationOutput)

####### Individual tests #######

# KS test for correct distribution of residuals
testUniformity(simulationOutput)

# KS test for correct distribution within and between groups
testCategorical(simulationOutput, testData$group)

# Dispersion test - for details see ?testDispersion
testDispersion(simulationOutput) # tests under and overdispersion

# Outlier test (number of observations outside simulation envelope)
# Use type = "boostrap" for exact values, see ?testOutliers
testOutliers(simulationOutput, type = "binomial")

# testing zero inflation
testZeroInflation(simulationOutput)

# testing generic summaries
countOnes <- function(x) sum(x == 1)  # testing for number of 1s
testGeneric(simulationOutput, summary = countOnes) # 1-inflation
testGeneric(simulationOutput, summary = countOnes, alternative = "less") # 1-deficit

means <- function(x) mean(x) # testing if mean prediction fits
testGeneric(simulationOutput, summary = means)

spread <- function(x) sd(x) # testing if mean sd fits
testGeneric(simulationOutput, summary = spread)

DHARMa documentation built on Oct. 18, 2024, 5:09 p.m.