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mxAlgebra(expression, name = NA, dimnames = NA)

mxAlgebra() allows you create algebraic expressions based on one or more MxMatrix objects. Legal functions are described here

Common misunderstandings are to call mxAlgebra expecting it to be run

To evaluate an MxAlgebra, it must be placed in an MxModel (along with all referenced MxMatrix objects) and run.

A <- mxMatrix("Full", nrow = 3, ncol = 3, values=1:9, name = "A")
B <- mxAlgebra(A, name = "B")
C <- mxAlgebra(A + B, name = "C")
D <- mxAlgebra(sin(C), name = "D")
model <- mxModel("AlgebraExample", A, B, C, D )
fit   <- mxRun(model)
mxEval(AlgebraExample.D, fit)
#           [,1]       [,2]       [,3]
#[1,]  0.9092974  0.9893582  0.9906074
#[2,] -0.7568025 -0.5440211 -0.2879033
#[3,] -0.2794155 -0.5365729 -0.7509872

Gotchas

A common misunderstanding is to call mxAlgebra() expecting it to be evaluated without subsequently being placed in a model and run as above.