Matrix Generation

GAMS Transfer R stores data in a “flat” format, that is, one record entry per data frame row. However, it is often necessary to convert this data format into a matrix/array format. GAMS Transfer R enables users to do this with relative ease using the toDense symbol methods This method will return a dense N-dimensional array (matrix for 2-Dimensions) with each dimension corresponding to the GAMS symbol dimension; it is possible to output an array up to 20 dimensions (a GAMS limit).

Example (1D data w/o domain linking (i.e., a relaxed domain))

library(gamstransfer)
m <- Container$new()
a <- Parameter$new(m, "a", "i", records = data.frame(uni = c("a", "c"), element_text = c(1, 3)))

> a$toDense()
[1] 1 3

Note that the parameter a is not linked to another symbol, so when converting to a matrix, the indexing is referenced to the data structure in a$records. Defining a sparse parameter a over a set i allows us to extract information from the i domain and construct a very different dense matrix, as the following example shows:

library(gamstransfer)
m <- Container$new()
i <- Set$new(m, "i", records = c("a", "b", "c", "d"))
a <- Parameter$new(m, "a", i, records = data.frame(c("a", "c"), c(1, 3)))

> a$toDense()
[1] 1 0 3 0

Example (2D data w/ domain linking)

library(gamstransfer)
m <- Container$new()
i <- Set$new(m, "i", records = c("a", "b", "c", "d"))
a <- Parameter$new(m, "a", c(i, i),
records =
    data.frame(i = c("a", "c"), i = c("a", "c"), c(1, 3))
)

> i$records
    uni
1     a
2     b
3     c
4     d

> a$records
    i i.1 value
1   a   a     1
2   c   c     3

> a$toDense()
    [,1] [,2] [,3] [,4]
[1,]    1    0    0    0
[2,]    0    0    0    0
[3,]    0    0    3    0
[4,]    0    0    0    0

Note

If there are unused UELs in the domain symbol, toDense() requires that the unused UELs are at the end of UEL list. One can achieve this by calling the reorderUELs() method for the domain symbol. Similarly, if the symbol records are in a different order than that of domain symbol UEL, UELs should be reordered to follow the record order. This can also be achived using reorderUELs() symbol method.