Vega-lite: Easier control over chart font size

[pteehan]

I encountered this issue in Altair:

• I wish to make a big chart, say 800x600, for a presentation slide
• The font sizes do not scale with the chart and are too small for my needs
• I have to change the font size for the axis, legend, and facet, labels and titles each, a total of six places. Figuring out how to do this took a while, and it's quite a bit of code.

In R's ggplot2 you would do this to scale the fonts to size 18 - I think the default is 12.

ggplot(...) + theme_bw(base_size=18)

All the fonts are scaled relative to the base size - some are larger and some are smaller. From a usability perspective this is a really nice feature to have when making plots that are designed to be shared or published in some way.

[kanitw]

Thanks. baseFontSize might be a good name for this, but we need to sync with latest config/theme in Vega and probably make it consistent. #1638

[g3o2]

In Vega one would use signal to achieve this kind of effect, as the issue can concern any type of marks. In a higher level grammar this would probably be less intuitive, so what would be the typical vega-lite way?

[kanitw]

Moved to https://github.com/vega/vega-parser/issues/18

[mathiasleroy]

Since vega/vega-parser#18 is closed and doesn't solve the issue,
here are the properties that I had to change to enlarge a graph :

spec.width = 800;
spec.height = 500;
spec.config.axisY.titleFontSize = 14;
spec.config.axisX.titleFontSize = 14;
spec.config.axisY.labelFontSize = 16;
spec.config.axisX.labelFontSize = 16;
spec.title.fontSize = 20;
spec.encoding.color.legend.titleFontSize = 15;
spec.encoding.color.legend.labelFontSize = 15;

(spec is the whole json object)

[pierre-haessig]

Maybe the issue could be reopened then?

[domoritz]

If you want to make all fonts larger, you could also make the chart smaller and scale it up. Does that solve the original issue?

[pierre-haessig]

@domoritz yes it would solve it, but I only found so far the scaling option for saving charts (I'm using Altair: Figure Size/Resolution doc). I also see a scaleFactor in vega-embed, but it seems also for PNG/SVG rendering only.

[domoritz]

For Altair, this wouldn’t work as easily but if you want to embed a chart in a presentation, you can embed the graphic and resize it.

I agree that it would be nice to have a single place to change the font size. We would need to do it in Vega, though. Could you file an issue there?