Inconsistent behavior for Apply when using with ApplyDataFrameFn

[rocketlaunchr]

Inconsistent behavior for Apply when using with ApplyDataFrameFn

[pjebs]

https://godoc.org/github.com/rocketlaunchr/dataframe-go#Apply
https://godoc.org/github.com/rocketlaunchr/dataframe-go#ApplyDataFrameFn

[pjebs]

var ctx = context.Background()

func main() {

	csvStr := `contact_number_country_code,contact_number
"973","12345678"`

	df, _ := imports.LoadFromCSV(ctx, strings.NewReader(csvStr), imports.CSVLoadOptions{
		DictateDataType: map[string]interface{}{
			"contact_number_country_code": "",
			"contact_number":              "",
		},
	})

	sConcatContactNumber := dataframe.NewSeriesString("concat_contact_number", &dataframe.SeriesInit{Size: df.NRows()})
	df.AddSeries(sConcatContactNumber, nil)

	applyFn := dataframe.ApplyDataFrameFn(func(vals map[interface{}]interface{}, row, nRows int) map[interface{}]interface{} {
		return map[interface{}]interface{}{
			"concat_contact_number": vals["contact_number_country_code"].(string) + vals["contact_number"].(string),
		}
	})

	_, err := dataframe.Apply(ctx, df, applyFn, dataframe.FilterOptions{InPlace: true})
	if err != nil {
		log.WithError(err).Error("concatenation cannot be applied")
	}

	fmt.Println(df)
}

[pjebs]

@migscabral

Can you try the sample I wrote above.

The issue is when you return the vals. The return map indicates what you want to change.

The key of map accepts ints (for index of Series) or strings (for name of series).

In your erroneous case:

 vals: map[0:973 1:12345678 2:<nil> concat_contact_number:97312345678 contact_number:12345678 contact_number_country_code:973]

It is saying change second column to nil but also saying change concat_contact_number Series to "97312345678". They point to the same Series in your case.

Either use ints or strings when referring to Series but not both.

[migscabral]

@pjebs I updated my code to return a new map from inside ApplyDataFrameFn and it now works. Thank you.

I have several questions so I may understand better how this library works:

1. I'm not sure where in my code where the int or string keys were set. From what I understand I did not explicitly set to use the int or string keys. The vals map that was received by ApplyDataFrameFn already contained both. Can you point me where it was set?

2. The key difference that I saw between your implementation and mine is that you created a new map inside the ApplyDataFrameFn instead of directly modifying the vals map. Is this the recommended way?

[pjebs]

1. the vals param contains the existing values for the row with the key as an int (index) and string (name) for convenience.

2. The applyFn must return a map that contains only what you want to update. You were basically rereturning the current row values (and not just the changes to update). I have updated the documentation to make it clearer.

[migscabral]

Thank you @pjebs much clearer now. Do you have a link to the said documentation?

[pjebs]

let me refresh godocs.org