On Wed, 3 Jun 2009, Huihua Lu wrote:
Hi everyone,
I have trouble to use RWeka, I tried: (w=weather dataset, all
preditors are nominal)
m<-J48(play~., data=w)
e<-evaluate_Weka_classifier(m,cost = matrix(c(0,2,1,0),
+ ncol = 2),numFolds = 10, complexity = TRUE,seed = 123,
+ class = TRUE)
it gives me exactly what I want, but when I tried the same classifier
on the other published data: (iris dataset has all numeric preditors)
m<-J48(Species~., data=iris)
e <- evaluate_Weka_classifier(m,
+ cost = matrix(c(0,2,1,0), ncol = 2),
+ numFolds = 10, complexity=TRUE, class=TRUE)
it threw me the error as below:
Error in .jnew("weka/classifiers/Evaluation", instances, costMatrix) :
Failed to create object of class `weka/classifiers/Evaluation'
In addition: Warning message:
In .jnew("weka/classifiers/Evaluation", instances, costMatrix) :
NewObject
("weka/classifiers/Evaluation","(Lweka/core/Instances;Lweka/classifiers
/CostMatrix;)V",...) failed
I know there are something wrong in the function of
evaluate_Weka_classifier, but I am stuck. Any one can help me out?
Is it because the attributes of predictors? then, how can I set up
the parameters in evaluat_Weka_classifier function? Thanks very much!
For me, it throws one more error, that you didn't include:
Exception in thread "main" java.lang.Exception: Cost matrix not compatible
with data!
at weka.classifiers.Evaluation.<init>(Unknown Source)
Your response has three levels, hence the cost matrix needs to be 3x3.
e <- evaluate_Weka_classifier(m,
cost = matrix(c(0, 1, 2, 2, 0, 1, 1, 1, 0), ncol = 3),
numFolds = 10, complexity=TRUE, class=TRUE)
works correctly but throws a warning. This warning is not critical,
though, and should be fixed in the next RWeka version.
Best,
Z
lu
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