I am writing some functions that need to select some submatrices with variable indices. Let's consider the following sample code. The issue is that mxModel() only recognizes x in the gobal environment rather than inside a function. Have I missed something? Thanks.
myFun <- function() {
x <- 2
cat("Matrix in R:\n")
A1 <- matrix(1:16, ncol=4, nrow=4)
B1 <- A1[1:x,1:x, drop=FALSE]
print(B1)
myModel <- mxModel("test",
A2 <- mxMatrix("Full", nrow=4, ncol=4, values=1:16, name="A2"),
B2 <- mxAlgebra(A2[1:x, 1:x], name="B2"))
cat("Matrix in mxModel:\n")
print(mxEval(B2, mxRun(myModel, silent=TRUE)))
}
myFun()
Matrix in R:
[,1] [,2]
[1,] 1 5
[2,] 2 6
Matrix in mxModel:
Error in print(mxEval(B2, mxRun(myModel, silent = TRUE))) :
error in evaluating the argument 'x' in selecting a method for function 'print': Error: Unknown reference 'x' detected in the entity 'B2' in model 'test'
x <- 3
myFun()
Matrix in R:
[,1] [,2]
[1,] 1 5
[2,] 2 6
Matrix in mxModel:
[,1] [,2] [,3]
[1,] 1 5 9
[2,] 2 6 10
[3,] 3 7 11
sessionInfo()
R version 2.15.2 (2012-10-26)
Platform: i686-pc-linux-gnu (32-bit)
#
locale:
[1] LC_CTYPE=en_SG.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_SG.UTF-8 LC_COLLATE=en_SG.UTF-8
[5] LC_MONETARY=en_SG.UTF-8 LC_MESSAGES=en_SG.UTF-8
[7] LC_PAPER=C LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_SG.UTF-8 LC_IDENTIFICATION=C
#
attached base packages:
[1] stats graphics grDevices utils datasets methods base
#
other attached packages:
[1] OpenMx_1.3.1-2179
#
Hi Mike
I think I got around this type of problem with the following:
YMMV of course (not sure if it will work for you), but perhaps this will help.
Thanks Michael and Ralf.
I will use eval(parse()) for the time being.
I think the simplest solution would be to define x in the global environment, this can be done inside the function by using
x <<- 2
Otherwise there are possibilities to use, as Mike pointed out, paste and eval functions. Timothy Brick wrote about this in a previous thread: http://openmx.psyc.virginia.edu/thread/1096
Another way to do it is: