Add homeland coords for language groups ...

[xrotwang]

... computed as "minimal distance" as described in "Testing methods of linguistic homeland detection using synthetic data" https://doi.org/10.1098/rstb.2020.0202

[xrotwang]

@d97hah This might be a useful addition as far as

• it adds geocoords for each family languoid
• it does so in a cheap yet principled way

Thoughts?

[xrotwang]

Implementation:

"""
Testing methods of linguistic homeland detection using synthetic data
Søren Wichmann and Taraka Rama
https://doi.org/10.1098/rstb.2020.0202
"""
import random
import collections

import pyproj
from pycldf import Dataset

def geodist(geod, p1, p2):
    return geod.inv(p1[1], p1[0], p2[1], p2[0])[2]

def md(g, coords):
    if len(coords) == 1:
        return coords[0]
    if len(coords) == 2:
        return random.choice(coords)
    random.shuffle(coords)
    mindist, mincoord = None, None

    for i, coord in enumerate(coords):
        dist = sum(geodist(g, coord, p) for j, p in enumerate(coords) if i != j)
        if (mindist is None) or (dist < mindist):
            mindist, mincoord = dist, coord
    return mincoord

if __name__ == '__main__':
    cldf = Dataset.from_metadata('cldf/cldf-metadata.json')
    subgroups = collections.defaultdict(list)
    vals = [v for v in cldf['ValueTable'] if v['Parameter_ID'] in ['level', 'classification']]

    # Find language-level languoids with coordinates:
    languages = {
        v['Language_ID'] for v in vals
        if v['Parameter_ID'] == 'level' and v['Code_ID'] == 'level-language'}
    languages_with_coords = {
        l['ID']: (l['Latitude'], l['Longitude'])
        for l in cldf['LanguageTable'] if l['ID'] in languages and l['Latitude'] is not None}
    names = {l['ID']: l['Name'] for l in cldf['LanguageTable']}

    # Collect sets of languages per language family/subgroup:
    for v in vals:
        if (v['Language_ID'] in languages_with_coords) and (v['Parameter_ID'] == 'classification'):
            clf = v['Value'].split('/')
            for i, _ in enumerate(clf, start=1):
                subgroups[' '.join(clf[:i])].append(languages_with_coords[v['Language_ID']])

    # Compute minimal distances per group:
    g = pyproj.Geod(ellps='WGS84')
    for group, coords in sorted(subgroups.items(), key=lambda i: ','.join(names[gc] for gc in i[0].split())):
        print('{}\t{}\t{}\t{}'.format(*[','.join(names[gc] for gc in group.split())] + list(md(g, coords)) + [len(coords)]))

[d97hah]

The classic principle of max diversity seems to have these properties but with better principles, i.e., in practice:

• The homeland of a family is the point with the shortest distance to the (inferred) location of its immediate daughters (recursively)
• A cheap approximation to this is to take lat = avg([lat for (lat, lon) in daughters]), lon = avg([lon for (lat, lot) in daughters])
• If the resulting point is in water, take the nearest point on land to this

all the best, H

Pada tanggal Kam, 13 Okt 2022 pukul 09.18 Robert Forkel < @.***> menulis:

@d97hah https://github.com/d97hah This might be a useful addition as far as

• it adds geocoords for each family languoid
• it does so in a cheap yet principled way

Thoughts?

— Reply to this email directly, view it on GitHub https://github.com/glottolog/glottolog-cldf/issues/14#issuecomment-1277140656, or unsubscribe https://github.com/notifications/unsubscribe-auth/AA2QHSD2BLCW6BJLOKIBIEDWC6ZTTANCNFSM6AAAAAARD64SS4 . You are receiving this because you were mentioned.Message ID: @.***>

[xrotwang]

The "take the nearest point on land" bit seems non-trivial, though. The "minimal distance" approach gets around this in a somewhat crude way - but it comes with a citation to justify the approach :)

[xrotwang]

Arguably, though, having a coordinate for a language group on water, isn't completely non-sensical. It comes with the "the ancestors passed through here" connotation.

Anyway, I think it wouldn't be a problem to add more ways to infer homelands lateron. (We'd like to get coordinates for proto-languages right now for Steve's bdproto - and the "minimal distance" ones would do the trick :) )

[xrotwang]

I'll try to whip up a "max diversity" algorithm accepting locations on water and plot the results.

[xrotwang]

Found a fairly simple (and amazingly fast) solution to the "nearest point on land" problem. Will send around results soon.

[d97hah]

Great, I have something similar implemented somewhere but you, as usual, were faster! H

Pada tanggal Jum, 14 Okt 2022 pukul 09.53 Robert Forkel < @.***> menulis:

Found a fairly simple (and amazingly fast) solution to the "nearest point on land" problem. Will send around results soon.

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[xrotwang]

My implementation is basically this:

    from shapely.geometry import MultiPoint
    from shapely.ops import nearest_points

    cent = MultiPoint([(p[1] + 360 if p[1] < 0 else p[1], p[0]) for p in coords]).convex_hull.centroid
    homeland = nearest_points(land, cent)[0]
    return (homeland.y, homeland.x - 360 if homeland.x > 180 else homeland.x)

where land is the MultiPolygon from https://geojson-maps.ash.ms/

[xrotwang]

@d97hah to get rid of the weirdest effects of languages like Hunsrik, one could limit the eligible languages for homeland computation to certain combinations of macroareas. Do you think that makes sense? E.g. exclude the Americas whenever there's other macroareas involved?

[xrotwang]

Looking over the families, a simple blacklist of macroareas for Atlantic-Congo, Austronesian and Indo-European would probably be enough, though.

[xrotwang]

@d97hah do you have a citation for this method of computing homelands? It isn't exactly the "diversity" method presented in Wichmann 2015.

[xrotwang]

Wikipedia sees to cite Campbell 2013 for this.

[d97hah]

It goes back to Sapir and there's also a botanical analogue by someone called Vavrilov (?, from memory). Neither has the 'in water' twist. It's enough to cite Campbell 2013 I think, which should contain refs to the history.

Pada tanggal Jum, 14 Okt 2022 pukul 15.55 Robert Forkel < @.***> menulis:

Wikipedia sees to cite Campbell 2013 https://glottolog.org/resource/reference/id/547852 for this.

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[xrotwang]

Ok, I'll update #15 to include these homelands.