Hi, I'm new here,
I'd like to map a set of values in a data frame to another set of values in
another frame (think a c++ map<>, a python dict or a hash lookup)
Specifically, I have a data frame of information about trading periods in the
NZ electricity market. For each period I have information about each bus (or
node) in the network. I'd like add a "column" to the data frame containing the
island that the bus is on.
I'm afraid my success at searching for an answer is restricted by not knowing
what this operation might be called in R, but I found a something on
stackoverflow [1] and tried the following:
map <- read.table("../node_islands.csv", header=TRUE, sep=",")
map <- setNames(map$island, map$node)
periods$Island = map[periods$Bus]
Where after the first line, but before the second and third:
> map[1:3,]
node island
1 ABY0111 SI
2 ABY1101 SI
3 ADD0111 SI
and:
> periods[1:3, c("Date", "Period", "Bus", "Price")]
Date Period Bus Price
1 2004-01-01 1 ABY0111 31.20
2 2004-01-01 1 ADD0111 32.43
3 2004-01-01 1 ADD0661 32.38
This seems to work (it fooled me for quite a while :-) ), but the following
check:
for (b in periods$Bus)
{
if (periods[periods$Bus == b, "Island"] != map[b])
{
print(b)
print(periods[periods$Bus == b, "Island"][1:1])
print(map[b])
}
}
prints a number of lines where periods$Island does not match the corresponding
value in map:
[1] "ALB0331"
[1] SI
Levels: NI SI
ALB0331
NI
Levels: NI SI
[1] "APS0111"
[1] NI
...
Clearly, I've missed the point here. Would anyone be so kind as help me find
it or suggest which FM I might need to R?
Cheers,
Geoff
[1]
http://stackoverflow.com/questions/7547597/dictionary-style-replace-multiple-items-in-r
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