Description Usage Arguments Details Value Author(s)

Function `getAmatrix`

finds A-matrices used to express ANOVA sum of squares as quadratic forms in *y*.

1 | ```
getAmatrix(X1, X2)
``` |

`X1` |
(matrix) lower order model matrix (comprising all factors entering model before 'X2'-factor) |

`X2` |
(matrix) higher order model matrix (entering model after 'X1' factors) |

Compute A-Matrix for expressing ANOVA Type-1 sequential sum of squares *SS* as quadratic form in *y* (column vector of observations),
*y' * A * y = SS*.
In random models, when the intercept is the only fixed effect, the design matrix of fixed effects is equal to a column vector
where each element is equal to one (1). In this setting, it holds *1' * A * 1 = 0*, i.e. all elements of A summing to zero.

This function is not intended to be used directly.

(matrix) for obtaining quadratic forms in *y* expression ANOVA sum of squares

Andre Schuetzenmeister [email protected]

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