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## This behavior is purposeful. We made a design decision to not allow mxPath
## to create simultaneous single headed and double headed arrows in the same
## position in the A and S matrices. The rare (really, are there any?) cases
## when this makes sense are far outweighed by the times when people are either
## (a) making a mistake or (b) trying to convert a single headed into a double
## headed arrow or vice versa. Of course, this behavior can be overridden by
## directly manipulating an mxMatrix. We did (and I do still) consider mxPath()
## to be the training wheels for OpenMx. The idea being we would like to make
## it difficult to make mistakes. I believe this philosophy is still correct.
##
## https://lists.virginia.edu/sympa/arc/openmx-developers/2016-03/msg00085.html
# "~/bin/OpenMx/inst/models/failing/check_RAM_paths_dont_overwrite.R"
# When adding paths in mxModel, I think everything the user requests should be added
# in line with what you say is what you get?
m1 <- mxModel("x_to_y_is_OK", type="RAM",
manifestVars = c("X", "Y"),
# both these paths should be added:
mxPath("X", to = "Y", arrows = 1)
)
# X->Y is fine
omxCheckEquals(m1$A$free["Y","X"], TRUE)
m1 <- mxModel("x_with_y_overwrites_x_to_y", type="RAM",
manifestVars = c("X","Y"),
# both these paths should be added:
mxPath("X", to = "Y", arrows = 1),
mxPath("X", to = "Y", arrows = 2)
)
# Oops: the 2-headed path overwrote the 1-headed path
omxCheckEquals(m1$A$free["Y","X"], TRUE)
# Last-path-in is OK
omxCheckEquals(m1$S$free["Y","X"], TRUE)
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