Hello,
Try, after the first instruction but before the second and third,
merge(periods, map, by.x="Bus", by.y="node", all.x=TRUE)
Also, it's better to use dput() to give data examples. To paste the
output of this or similar in a post is the recomended way:
dput(head(periods, 20)) # or 30, or enough to be representative
Hope this helps,
Rui Barradas
Em 12-06-2012 03:27, Geoff Leyland escreveu:
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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