Average commodity cost report

Ref: #1015

Something that ~~does not exist out-of-the-box in Ledger but~~ would be very convenient. After implementing the lots feature, and pricing in another commodity (-X), this should be trivial as the value is already "there somewhere". It would need to be output with an appropriate switch.

Effectively, given the data https://gitlab.com/snippets/1856416 one should be able to get an average cost of the commodity in another commodity (currency).

In practice, this means that I want to know that,

after initial purchase on 2019-01-12, the average cost of 1 ETF held was (the original cost) 10 EUR
after second purchase, on 2019-01-20, the average cost per unit for ETF held was 11 EUR, (5 @ 10 EUR + 5 @ 12 EUR)

This shows the average cost/price per unit for the available lots. The total value is available after --unrealized implementation.

Test case

command b --lots --flat result

          980.00 EUR  Assets:Cash
4 ETF {12.00 EUR} [2019-01-15]  Assets:Shares
          -28.00 EUR  Capital Gains
        -1000.00 EUR  Equity:Opening Balances
--------------------
4 ETF {12.00 EUR} [2019-01-15]
          -48.00 EUR

The remaining 4 ETF lot is from the lot [2019-01-15] and its avg. cost (= original cost in this case) is 12 EUR.

A more complex case would be appropriate for this, to show the average of multiple lots involved.

simonmichael / hledger

Average commodity cost report #1020

Test case