On Sat, 3 Jan 2015, David Winsemius wrote:
On Jan 3, 2015, at 1:21 AM, Rodica Coderie via R-help wrote:
Hello,
Can the decisions tree rules be exported? Along with the probabilities
associated with each node?For example, I've created a CHAID decision with a
target variable RESPONSE (YES/NO). I have 17 inner nodes with 19 terminal
nodes. How which terminal node has the highest probability of YES and which is
the probability?
An example of a terminal node output is below:clicks_flag in YES: NO (n = 1142,
err = 5.3%)
Thanks!Rodica
[[alternative HTML version deleted]]
When posting on the weekends it is particularly important to follow the
guidelines in the Posting Guide. Many of us who regularly monitor the
list will ignore questions that do not have library calls to the
packages needed and code to produce a reproducible example. (And you
should learn to post in plain text rather than HTML.)
Yes, a reproducible example would have been good.
I assume you are talking about the "CHAID" package from R-Forge. We
haven't got a nice and ready to use function in "partykit" (which "CHAID"
is built upon) but we have an unexported .list.rules.party function
which does a good part of what you want to do.
## package and data
library("CHAID")
ucb <- as.data.frame(UCBAdmissions)
ucb <- ucb[rep(1:nrow(ucb), ucb$Freq), 1:3]
## fit tree
ch <- chaid(Admit ~ Gender + Dept, data = ucb)
plot(ch)
print(ch)
## get rule path
partykit:::.list.rules.party(ch)
And with that information it is not too hard to set something up that is
close to what you want, I think:
format_rules <- function(object, ...) {
ft <- fitted(object)
ns <- tapply(ft[[2]], ft[[1]], length)
pr <- tapply(ft[[2]], ft[[1]], function(y)
min(prop.table(table(y))))
lb <- tapply(ft[[2]], ft[[1]], function(y)
names(sort(table(y), decreasing = TRUE))[1])
rl <- partykit:::.list.rules.party(object)
paste0(rl, ": ", lb, " (n = ", ns, ", ", round(100 * pr, 2), "%)")
}
writeLines(format_rules(ch))
hth,
Z
--
David Winsemius
Alameda, CA, USA
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
