Domain Forwarding

GAMS includes the ability to define sets directly from data using the implicit set notation (see: implicit set definition ). This notation has an analogue in GAMS Transfer R called domainForwarding.

Note

It is possible to recursively update a subset tree in GAMS Transfer R.

Domain forwarding is available as an argument to all symbol object constructors; the user would simply need to pass domainForwarding=TRUE to forward domain across all dimensions or as a logical vector domainForwarding=c(TRUE, FALSE,….) to forward domain across selected dimensions.

In this example, we have raw data that is in the dist data frame, and we want to send the domain information into the i and j sets. We take care to pass the set objects as the domain for parameter c.

library(gamstransfer)
m <- Container$new()
i <- Set$new(m, "i")
j <- Set$new(m, "j")

dist <- data.frame(
from = c(
    "seattle", "seattle", "seattle",
    "san-diego", "san-diego", "san-diego"
),
to = c(
    "new-york", "chicago", "topeka",
    "new-york", "chicago", "topeka"
),
thousand_miles = c(2.5, 1.7, 1.8, 2.5, 1.8, 1.4)
)

c <- Parameter$new(m, "c", c(i, j), records = dist, domainForwarding = TRUE)

> i$records
        uni
1   seattle
2 san-diego

> j$records
    uni
1 new-york
2  chicago
3   topeka

> c$records
    from       to value
1   seattle new-york   2.5
2   seattle  chicago   1.7
3   seattle   topeka   1.8
4 san-diego new-york   2.5
5 san-diego  chicago   1.8
6 san-diego   topeka   1.4

Note

The element order in the sets i and j mirrors that in the raw data.

We can also selectively use domainForwarding for part of the domain by passing a logical vector to the domainForwarding argument as shown in the following example. The domain records are forwarded only to the domain set i but not to the domain set j.

library(gamstransfer)
m <- Container$new()
i <- Set$new(m, "i")
j <- Set$new(m, "j")

dist <- data.frame(
from = c(
    "seattle", "seattle", "seattle",
    "san-diego", "san-diego", "san-diego"
),
to = c(
    "new-york", "chicago", "topeka",
    "new-york", "chicago", "topeka"
),
thousand_miles = c(2.5, 1.7, 1.8, 2.5, 1.8, 1.4)
)

c <- Parameter$new(m, "c", c(i, j), records = dist, domainForwarding = c(TRUE, FALSE))

> i$records
        uni
1   seattle
4 san-diego

> j$records
NULL

> c$records
    from       to value
1   seattle new-york   2.5
2   seattle  chicago   1.7
3   seattle   topeka   1.8
4 san-diego new-york   2.5
5 san-diego  chicago   1.8
6 san-diego   topeka   1.4

In this example, we show that domain forwarding will also work recursively to update the entire set lineage. The domain forwarding occurs at the creation of every symbol object. The correct order of elements in set i is (z, a, b, c) because the records from j are forwarded first, and then the records from k are propagated through (back to i).

library(gamstransfer)
m <- Container$new()
i <- Set$new(m, "i")
j <- Set$new(m, "j", i, records = c("z"), domainForwarding = TRUE)
k <- Set$new(m, "k", j, records = c("a", "b", "c"), domainForwarding = TRUE)

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

> j$records
    i
1   z
2   a
3   b
4   c

> k$records
    j
1   a
2   b
3   c