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eriknw opened this issue May 23, 2022 · 3 comments · May be fixed by #257
Open

Apply dict to map values #246

eriknw opened this issue May 23, 2022 · 3 comments · May be fixed by #257
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enhancement Improve existing functionality or make things work better lowpriority

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@eriknw
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eriknw commented May 23, 2022

This is probably a crazy idea (and I don't currently have a use case), but could we make it easy to apply a dict to map values? For example, to make the following easier and more reliable (i.e., not rely on inlining the dict):

In [10]: v = gb.Vector.from_values(np.arange(5), np.arange(5))

In [11]: v
Out[11]:
"v_2"      nvals  size  dtype  format
gb.Vector      5     5  INT64    full
-------------------------------------
index  0  1  2  3  4
value  0  1  2  3  4

In [12]: v.apply(lambda x: {0: 0, 1: 2, 2: 4, 3: 6, 4: 8}[x]).new()
Out[12]:
"v_4"      nvals  size  dtype  format
gb.Vector      5     5  INT64    full
-------------------------------------
index  0  1  2  3  4
value  0  2  4  6  8

This requires Numba to know the types of the dictionary. Also, I don't know how easy it would be to have a default value. This may require its own method.

This is inspired by the Pandas functionality to be able to use x.map(d) to apply a dict or Series mapping.
@eriknw eriknw added enhancement Improve existing functionality or make things work better lowpriority labels May 23, 2022
@eriknw eriknw linked a pull request Jun 4, 2022 that will close this issue
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@SultanOrazbayev
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I think using dicts is a bit counter-intuitive here. In the spirit of working with matrix representations, wouldn't we want to express this as a matrix operation (via permutation matrix, that could be constructed from dict)?

@eriknw
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eriknw commented Dec 7, 2022

Thanks for reading our issues and commenting @SultanOrazbayev :)

My initial description of and examples for this operation confused @jim22k too. See more discussions in #257

For example, say you wanted to change all 2 values in your matrix to 4 (and let's ignore what happens to the other values for now). This issue proposes "applying a dict mapping" as e.g. A.applymap({2: 4}).

Make sense? We're not doing a permutation, and we're not treating the dict as a matrix.

@SultanOrazbayev
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OK, I see now. I misread the example to change the indexes, so for mapping values using dict makes sense.

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Map values according to a dict eriknw/grblas
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