How to use tidyverse to group columns

[mara]

@blackish952

Even if we just look at 2018, there are 6 rows for customer number 0 but your code output gave me 3 distinct invoice number, which is great.
But then I cannot calculate the total invoice per each distinct invoice.

Can we achieve this goal?

You can do multiple groupings to calculate summaries and totals. See, for example, the Grouping section in ModernDive (link below)
http://moderndive.com/5-wrangling.html#groupby

Also, please try to use the reprex package rather than code + screenshots! It's much easier to go back and forth that what.
For pointers specific to the community site, check out the reprex FAQ.