frequencies for more than 1 facettes/text-types

[hpreki]

This was part of Theresa Zieglers feature-list (and which is available in her Excel-Dashboard).

Multi-level-frequencies

Multi-level-frequencies are supported by NoSke - actually corpsum now uses the method freqs_ml which stands for multi-level.

This entails we nee to implement:

• 1. a way to actually specify a query for multi-level frequencies
     -- either: add it to list of predefined searches to the dashboard (but then: what would be the list of necesssary+useful combinations? year+region and year+docsrc quite obviously. But what else? => linguists must tell!)
     -- or: actually allow for a "free specification" of freq-parameters like in the NoSke)
• 2. a way to normalize the results: a crucial matter: NoSke nowadays provides correct normalisation but only for frequencies for 1 facette/text-type!
• 3. a way to present the results: 3D plots? In Theresas dashboard: a series of 2D plots. E.g. freqs for 5 x region + 20 x year: 5 plots (1 per region) with a extra plot per region with a 2D line plot "freqs over time"

[ctot-nondef]

this needs more user research,

• which specific combination of facets are needed?
• what would a good result representation?

some scenarios can already be handled in the current corpsum version, but need a lot click work
the sketch engine itself does not handle normalisation for multi facetted searches