On May 12, 2011, at 5:41 PM, John Dennison wrote:

Having poked the problem a couple more times it appears my issue is that the object i save within the loop is not available after the function ends. I
have no idea why it is acting in this manner.


library(rpart)

# grow tree
fit <- rpart(Kyphosis ~ Age + Number + Start,
method="class", data=kyphosis)
#predict
prediction<-predict(fit, kyphosis)

#misclassification index function

results<-as.data.frame(1)

predict.function <- function(x){
 j<-0
for (i in 1:length(kyphosis$Kyphosis)) {
if (((kyphosis$Kyphosis[i]=="absent")==(prediction[i,1]==1)) == 0 ){

j<-j+1
results[j,]<-row.names(testing[c(i),])

Are we supposed to know where to find 'testing" (and if we cannot find it, how is the R interpreter going to find it)?


print( row.names(kyphosis[c(i),]))
} }
{
print(results)
save(results, file="results") } }


i can load results from file and my out put is there. how ever if i just type results i get the original 1. what is in the lords name is occurring.

Thanks

John



On Thu, May 12, 2011 at 1:50 PM, Phil Spector <spec...@stat.berkeley.edu >wrote:

John -
 In your example, the misclassified observations (as defined by
your predict.function) will be

kyphosis[kyphosis$Kyphosis == 'absent' & prediction[,1] != 1,]

so you could start from there.
                                      - Phil Spector
                                       Statistical Computing Facility
                                       Department of Statistics
                                       UC Berkeley
                                       spec...@stat.berkeley.edu



On Thu, 12 May 2011, John Dennison wrote:

Greetings R world,

I know some version of the this question has been asked before, but i need to save the output of a loop into a data frame to eventually be written to
a
postgres data base with dbWriteTable. Some background. I have developed classifications models to help identify problem accounts. The logic is
this,
if the model classifies the record as including variable X and it turns
out
that record does not have X then it should be reviewed(ie i need the row
number/ID saved to a database). Generally i want to look at the
misclassified records. This is a little hack i know, anyone got a better
idea please let me know. Here is an example

library(rpart)

# grow tree
fit <- rpart(Kyphosis ~ Age + Number + Start,
method="class", data=kyphosis)
#predict
prediction<-predict(fit, kyphosis)

#misclassification index function

predict.function <- function(x){
for (i in 1:length(kyphosis$Kyphosis)) {
#the idea is that if the record is "absent" but the prediction is
otherwise
then show me that record
if (((kyphosis$Kyphosis[i]=="absent")==(prediction[i,1]==1)) == 0 ){
#THIS WORKS
print( row.names(kyphosis[c(i),]))
}
} }

predict.function(x)

Now my issue is that i want to save these id to a data.frame so i can
later
save them to a database. This this an incorrect approach. Can I save each
id
to the postgres instance as it is found. i have a ignorant fear of lapply,
but it seems it may hold the key.


Ive tried

predict.function <- function(x){
results<-as.data.frame(1)
for (i in 1:length(kyphosis$Kyphosis)) {
#the idea is that if the record is "absent" but the prediction is
otherwise
then show me that record
if (((kyphosis$Kyphosis[i]=="absent")==(prediction[i,1]==1)) == 0 ){
#THIS WORKS
results[i,]<- as.data.frame(row.names(kyphosis[c(i),]))
}
} }

this does not work. results object does not get saved. Any Help would be
greatly appreciated.


Thanks

John Dennison

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and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT

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