Add “Unit” so we automatically append units to axis & legend title.

[kanitw]

In an attempt to make axis title nicer, maybe we add fieldDef.unit or allow describing unit in the schema once we support it (#512).

For example, if fieldDef.unit is ’$’ for mean of ’cost’, the axis title could be ’MEAN(cost) (in $)’.

[ayush29feb]

@kanitw is this what you want to?

[domoritz]

We already use a similar syntax for aggregation functions. I think there are two options here. One is to write "Year in years" and the other is to show the unit with the data on the axis (acceptable for short units such as $).

[kanitw]

Good question! Here is what I think:

• unit as part of a field can be considered equivalent to having unit included from the schema.
• We could introduce showUnit as a property to axis and have these possible values: 'none', 'title' (Showing "Year in years" for the axis title), 'label-prefix' (Showing $100), 'label-suffix` ('Show 100 kg).

@domoritz -- what do you think?

[domoritz]

Sounds reasonable.
On Jan 23, 2016 19:49, "Kanit Wongsuphasawat" notifications@github.com
wrote:

Good question! Here is what I think:

• unit as part of a field can be considered equivalent to having unit
  included from the schema.
• We could introduce showUnit as a property to axis and have these
  possible values: 'none', 'title' (Showing "Year in years" for the axis
  title), 'label-prefix' (Showing $100), 'label-suffix` ('Show 100 kg).

@domoritz https://github.com/domoritz -- what do you think?

—
Reply to this email directly or view it on GitHub
#817 (comment).

[kanitw]

Cool. To summarize,

• add unit to fieldDef (interface & schema)
• add showUnit as enum to axis (interface & schema). This should be an enum with four values above. The default should be 'title' IMHO. See fieldDef.schema.ts's type for an example of how we declare enum and see config.schema.ts for how to declare default.
  • For 'title' case, modify model.fieldTitle()
  • For label-prefix/suffix, need to modify axis.ts's properties.labels. Probably need to use output's text's template property.

[ayush29feb]

I am a little confused why we have the showUnit in fieldDef.axis and unit in fieldDef

"encoding": {
    "y": {
      "field": "b2",
      "type": "quantitative",
      "unit": "$",
      "axis": {"showUnit": "label-prefix"}
    },
    "x": {"field": "a","type": "ordinal"}
  }

it seems a little weird to define that the unit would be in title inside axis

"encoding": {
    "y": {
      "field": "b2",
      "type": "quantitative",
      "unit": "Pounds",
      "axis": {"showUnit": "title"}
    },
    "x": {"field": "a","type": "ordinal"}
  }

How about this

"encoding": {
    "y": {
      "field": "b2",
      "type": "quantitative",
      "showUnit": {
       "unit": "Pounds",
       "position": "title" 
      }
    },
    "x": {"field": "a","type": "ordinal"}
  }

[ayush29feb]

If we plan to procced as @kanitw suggested, I am having some trouble accessing axis.showUnit in fieldDef.title method because there is not axis object in the title method

[kanitw]

Instead of calling fieldDef.title directly you can either make a new axis.title() or pass unit as a parameter to fieldDef.title. (Pick one that seems more appropriate – if you're unsure, let me know -- I can take a closer look.)

[kanitw]

Note: An early attempt of this was in #1301.

[kanitw]

It's easy enough to use title/format to do this, so let's close this.