contr.orthonorm: Orthonormal Contrast Matrices for Bayesian Estimation

Description Usage Arguments Details Value References Examples

View source: R/contr.orthonorm.R

Description

Returns a design or model matrix of orthonormal contrasts such that the marginal prior on all effects is identical. Implementation from Singmann & Gronau's bfrms, following the description in Rouder, Morey, Speckman, & Province (2012, p. 363).

Though using this factor coding scheme might obscure the interpretation of parameters, it is essential for correct estimation of Bayes factors for contrasts and order restrictions of multi-level factors (where k>2). See info on specifying correct priors for factors with more than 2 levels in the Bayes factors vignette.

Usage

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Arguments

n

a vector of levels for a factor, or the number of levels.

contrasts

a logical indicating whether contrasts should be computed.

sparse

logical indicating if the result should be sparse (of class dgCMatrix), using package Matrix.

Details

When contrasts = FALSE, the returned contrasts are equivalent to contr.treatment(, contrasts = FALSE), as suggested by McElreath (also known as one-hot encoding).

Value

A matrix with n rows and k columns, with k=n-1 if contrasts is TRUE and k=n if contrasts is FALSE.

References

Examples

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contr.orthonorm(2) # Q_2 in Rouder et al. (2012, p. 363)

contr.orthonorm(5) # equivalent to Q_5 in Rouder et al. (2012, p. 363)

## check decomposition
Q3 <- contr.orthonorm(3)
Q3 %*% t(Q3) ## 2/3 on diagonal and -1/3 on off-diagonal elements

DominiqueMakowski/bayestestR documentation built on July 27, 2021, 4:12 p.m.