* TODO Conversion to Spreadsheets
- State "TODO"       from              [2017-04-21 Fri 10:36]
This is a [[https://github.com/westonganger/spreadsheet_architect][gem]] that I can include into the Table model to convert a table into
a spread-sheet, or even a sheet in a multi-sheet spreadsheet file.

* TODO Add from_yql for fetching from Yahoo
- State "TODO"       from              [2017-04-21 Fri 10:35]
Add a constructor to allow fetching stock data from yql.  Perhaps grab all
available fields, then allow a select of those of interest.

* DONE Allow sorting by expression
CLOSED: [2022-01-20 Thu 12:47]
Either by a single string argument as the sole argument to order_by, or use
another method, such a order_with.  Note that this can be done now by creating
a new column having the sort expression with select and then just order_by
that column.  Perhaps that is an easy way to implement it.

* DONE Ensure that columns resulting from aggregates have proper type
CLOSED: [2017-12-29 Fri 05:34]
- State "WAIT"       from "TODO"       [2017-12-29 Fri 05:34]
- State "TODO"       from              [2017-11-27 Mon 04:46]
After applying avg, does the column have the proper Numeric or Date, or DateTime
type.  How about Boolean aggregates?

* DONE Formatters
CLOSED: [2017-04-21 Fri 10:36]
- State "WAIT"       from "TODO"       [2017-04-21 Fri 10:36]
- State "TODO"       from              [2017-04-21 Fri 10:35]
Need to think about ways to define formatters for Table for different output
types, including tty, color-tty, latex, csv, spreadsheet?

* DONE Add a Group Boundary concept
CLOSED: [2017-04-21 Fri 10:36]
- State "WAIT"       from "TODO"       [2017-04-21 Fri 10:36]
- State "TODO"       from              [2017-04-21 Fri 10:35]
If I want a table to perform sub-totals at various break points, need to have a
way for a table to record its grouping boundaries. Maybe an array of row
numbers?  Automatically injected by the group-by method?

* DONE Add uniq method and set operations
CLOSED: [2017-03-02 Thu 15:54]
- State "WAIT"       from "TODO"       [2017-03-02 Thu 15:54]
- State "TODO"       from              [2017-03-02 Thu 15:54]
For tables, add a method that eliminates any duplicate rows. Perhaps just apply
Array#uniq to the columns?