Add a index column to dataframe in gota - go

Question

with the following sample, I can add a new column that is diverted from the row values.
it's working well.
package main
import (
"fmt"
"strings"
"github.com/go-gota/gota/dataframe"
"github.com/go-gota/gota/series"
)
func main() {
csvStr := `accountId,deposit,Withdrawals
anil0001,50,10
vikas0002,10,10
ravi0003,20,10
user1111,NaN,20`
df := dataframe.ReadCSV(strings.NewReader(csvStr))
// Within a row, elements are indexed by their column index.
indexDeposit := 1
indexWithdrawals := 2
// Rapply reads the data by rows.
// You can access each element of the row using
// s.Elem(index) or s.Val(index).
// To browse by columns use Capply.
s := df.Rapply(func(s series.Series) series.Series {
deposit, err := s.Elem(indexDeposit).Int()
if err != nil {
return series.Ints("NAN")
}
withdrawal, err := s.Elem(indexWithdrawals).Int()
if err != nil {
return series.Ints("NAN")
}
return series.Ints(deposit - withdrawal)
})
// The new series is appended to
// the data source via a call to Mutate.
// You can print s to read its content.
df = df.Mutate(s.Col("X0")).
Rename("deposit_Withdrawals_diff", "X0")
fmt.Println(df)
}
but the question is that, I want to add an index ( row counter) to each row. ( later on I want to join it with a subset of that) So I need an index.
something like
index,accountId,deposit,Withdrawals
1,anil0001,50,10
2,vikas0002,10,10
3,ravi0003,20,10
4,user1111,NaN,20
I see there are no GetIndex or Index methods on series. How can I add this index?

Answer 1

I did it with a global variable ( but I'm not sure it's the best solution for gota, maybe for pure go developer is a good solution :) )
index := 0
s := df.Rapply(func(s series.Series) series.Series {
index++
return series.Ints(index)
})
df = df.Mutate(s.Col("X0")).
Rename("index", "X0")
fmt.Println(df)