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The dataset that I'm working on is unbalanced, so I'm trying to balance the dataset by undersampling but I get an error how to solve this error? here is the error that I got Error in function (formula, data, method, subset, na.action, N, P=0.5, : The response variable has only one class. how can solve this error?

What I have tried:

library(ROSE)

data_frame <- click.csv

data_frame2 <- buy.csv

colnames(data_frame) [1] "Session ID" "Timestamp" "Item ID" "Category"

colnames(data_frame2) [1] "Session ID" "Timestamp" "Item ID" "Price" "Quantity"

> mydata<- merge(x=data_frame, y=data_frame2, by = "SessionID", all.x = TRUE, allow.cartesian=TRUE)# left outer join mydata
> mydata
Session ID Timestamp.x Item ID.x Category Timestamp.y Item ID.y Price Quantity 1: 1 2014-04-07T10:51:09.277Z 214536502 0 2: 1 2014-04-07T10:54:09.868Z 214536500 0 3: 1 2014-04-07T10:54:46.998Z 214536506 0 4: 1 2014-04-07T10:57:00.306Z 214577561 0 5: 10000001 2014-09-08T10:35:38.841Z 214854230 S --- 40596049: 9999997 2014-09-07T18:12:46.466Z 214854159 S 40596050: 9999997 2014-09-07T18:13:04.315Z 214643036 S 40596051: 9999997 2014-09-07T18:14:47.365Z 214854159 S 40596052: 9999998 2014-09-07T20:53:43.120Z 214541597 0 40596053: 9999999 2014-09-04T04:44:46.942Z 214644650 S
mydataItemID.y[!is.na(mydataItemID.y[!is.na(mydataItemID.y)]<-1
mydataItemID.y[is.na(mydataItemID.y[is.na(mydataItemID.y)]<-0
table(mydata$ItemID.y)
0 1
29698257 10897796
str(mydata) Classes ‘data.table’ and 'data.frame': 40596053 obs. of 8 variables:SessionID:Factorw/9249729levels"1","10000001",..:1111222223...SessionID:Factorw/9249729levels"1","10000001",..:1111222223...Timestamp.x: Factor w/ 32937845 levels "2014-04-01T03:00:00.124Z",..: 1406509 1407501 1407712 1408409 29083768 29085345 29085440 29085649 29088238 29247009 ...ItemID.x:Factorw/52739levels"1178793047","1178794001",..:20832082208499065023064116410502305018748852...ItemID.x:Factorw/52739levels"1178793047","1178794001",..:20832082208499065023064116410502305018748852... Category : Factor w/ 339 levels "0","1","10","11",..: 1 1 1 1 339 339 339 339 339 339 ...Timestamp.y:Factorw/1136477levels"2014−04−01T03:05:31.743Z",..:NANANANANANANANANANA...Timestamp.y:Factorw/1136477levels"2014−04−01T03:05:31.743Z",..:NANANANANANANANANANA...ItemID.y : Factor w/ 2 levels "0","1": 1 1 1 1 1 1 1 1 1 1 ...Price:Factorw/735levels"0","10052","1015",..:NANANANANANANANANANA...Price:Factorw/735levels"0","10052","1015",..:NANANANANANANANANANA... Quantity : Factor w/ 28 levels "0","1","10","11",..: NA NA NA NA NA NA NA NA NA NA ... - attr(*, ".internal.selfref")
data_balanced_over <- ovun.sample(ItemID.y ~ ., data = mydata, method = "over",N = 800)
Error in function (formula, data, method, subset, na.action, N, P=0.5, :
The response variable has only one class.
Uwe Keim
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  • Welcome to StackOverflow! Please read the info about [how to ask a good question](http://stackoverflow.com/help/how-to-ask) and how to give a [reproducible example](http://stackoverflow.com/questions/5963269). This will make it much easier for others to help you. – Axeman Jul 03 '18 at 07:15
  • The answer is in your error `The response variable has only one class.` If your response variable only has one class, how can you undersample? You need more than one class. – MHammer Jul 03 '18 at 07:34
  • sir what do you mean by more than one class?? –  Jul 03 '18 at 07:44
  • You need to give us something to work with, use at least `dput(mydata)`..there are other ways you can simply undersample, look at `caret` package – RLave Jul 03 '18 at 08:07
  • Also, stop asking the same question with different account: https://stackoverflow.com/questions/51129796/dataset-balancing-error-using-ovun-sample https://stackoverflow.com/questions/51126377/error-in-balancing-dataset-via-oversampling – RLave Jul 03 '18 at 08:08

2 Answers2

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Since the example is not reproducibile, I suggest an alternative with a different function:

library(caret)
x <- matrix(mydata %>% select(-ItemId.y))
y <- as.factor(mydata$ItemId.y)
# x should be the matrix with your regressors
# y should be you factor response variable
downSample(x, y, yname = "ItemId.y") # will randomly sample a data set so that all classes have the same frequency as the minority class

Refer to downSample, for a working example.

RLave
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  • library(caret) x <- matrix(mydata %>% select(-ItemId.y) y <- as.factor(mydata$ItemId.y) # x should be the matrix with your regressors # y should be you factor response variable downSample(x, y, yname = "ItemId.y") Error in `$<-.data.frame`(`*tmp*`, .outcome, value = c(1L, 1L, 1L, 1L, : replacement has 40596053 rows, data has 7 –  Jul 03 '18 at 11:54
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Look in your x, that is, in your predictor variables, you probably have some that only have a single value.

Alejandro Zamudio Sosa
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  • Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Aug 31 '22 at 01:46