[BUG-REPORT] `get_groups` only returns the first group

[Ben-Epstein]

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Description The get_groups function only returns the first group passed in for the dataframe.

import numpy as np
import vaex

n=1000
label = np.random.randint(0, 20, size=n)
pred = np.random.randint(0,20,size=n)

data = {'label': label, 'pred': pred}
df = vaex.from_arrays(**data)

# The counts below will vary a bit because i'm generating random data, but the point remains
print(df.groupby("label").get_group([0]).count()) # 32
print(df.groupby("label").get_group([1]).count()) # 52
print(df.groupby("label").get_group([0,1]).count()) # 32
print(df.groupby("label").get_group([1,0]).count()) # 52
print(df.groupby("label").get_group([0,1])["label"].unique()) # [0]

Software information

• Vaex version (import vaex; vaex.__version__):

  {'vaex': '4.5.0',
  'vaex-core': '4.5.1',
  'vaex-viz': '0.5.0',
  'vaex-hdf5': '0.10.0',
  'vaex-server': '0.6.1',
  'vaex-astro': '0.9.0',
  'vaex-jupyter': '0.6.0',
  'vaex-ml': '0.14.0'}

• Vaex was installed via: pip / conda-forge / from source: pip
• OS: MacOS Big Sur (Intel Chip)

[maartenbreddels]

Hi Ben,

what should the expected behavior be, I don't fully understand what the issue is.

Regards,

Maarten

[Ben-Epstein]

@maartenbreddels I'd expect that when passing 2 or more values into get_group, you'd get the values for all groups. What we're seeing is that you only get the group for the first value in the list passed in.