I want to filter dataframe by column with Strings from different dataframe.

I have a dataframe like this :

I wish to create a dataframe by using a map such that the keys of the map are the column titles, and the values of the map are the data itself. In python and pyspark, this can be done quite easily in numerous ways- typically with one line of code, even-, but in Scala, I’m having serious trouble.

I read and filter data, need to count how each filter operation affects result.
Is it possible to somehow mixin spark accumulators while using Dataframe/Dataset api?

I have a variable like
val activityId = “activity_” + activityNum + “_id”
the variable activityNum is incremented from a loop (1,2,3,…)

I’m trying to compare the data from the same month but previous year and add previous year data to a new column ‘qty_ly’. As well as sum the last 3months of qty_cy for each product.