Limiting rows Since 0.16.5

Sometimes you may have a big, flat, data file where you may want to use some rows for one series and other rows for another. For series-based charts (e.g. scatter, line, bar, ridgeline) we can limit a particular series to only use certain rows by adding the where option to the series. This uses a very basic SQL-like syntax that can parse simple comparisons =, <, <=, >, >= and the boolean operators AND and OR.

For example, say we have a column titled London borough (that has the values either isLondon or notLondon in each row) and a numeric column titled vacants_per_thousand_dwellings. We can create multiple series from a flat file with something like the following:

series:
  - title: Outside London
    x: wage_ratio
    y: vacants_per_thousand_dwellings
    where: '"London borough"="notLondon" AND "vacants_per_thousand_dwellings"<50'
  - title: London
    x: wage_ratio
    y: vacants_per_thousand_dwellings
    where: '"London borough"="isLondon" AND "vacants_per_thousand_dwellings"<50'
  - title: Empties outside London
    x: wage_ratio
    y: vacants_per_thousand_dwellings
    where: '"London borough"="notLondon" AND "vacants_per_thousand_dwellings">=50'
  - title: Empties in London
    x: wage_ratio
    y: vacants_per_thousand_dwellings
    where: '"London borough"="isLondon" AND "vacants_per_thousand_dwellings">=50'