Add keyword arg to modelmatrix; define momentmatrix

src/regressionmodel.jl

@@ -46,7 +46,7 @@ function modelmatrix end
 Return `X'X` where `X` is the model matrix of `model`.
 This function will return a pre-computed matrix stored in `model` if possible.
 """
-crossmodelmatrix(model::RegressionModel) = (x = modelmatrix(model); Symmetric(x' * x))
+crossmodelmatrix(model::RegressionModel; kwarg...) = (x = modelmatrix(model; kwarg...); Symmetric(x' * x))
 
 """
     leverage(model::RegressionModel)

src/statisticalmodel.jl

@@ -314,3 +314,13 @@ function adjr2(model::StatisticalModel, variant::Symbol)
 end
 
 const adjr² = adjr2
+
+"""
+    momentmatrix(model::StatisticalModel)
+
+Return the matrix containing the estimating equation.
+
+For linear regression models, the moment matrix is given by u*X, where u is the vector of residuals and X is the model matrix.
+
+"""
+function momentmatrix end