R help - Feb 2021 - Different files for train and test data

Hi

I have two files of my data: part1 and part2. I used part1 to train and
test my data and got the RMSE value. Now I need to compare my obtained
result (RMSE value) with unseen data i.e. part2 of data. How can I use the
same training data of part1 and part2 data as test data.

I am using caret package.

d=readARFF("part1.arff")
index <- createDataPartition(d$price, p = .70,list = FALSE)
tr <- d[index, ]
ts <- d[-index, ]
......
.....
.....
.....
model <-train(price ~ ., data = tr,
method = "nnet",
metric = "RMSE",
trControl = ctr)

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