I have a Frame as follows:
x = dt.Frame(k = [1, 1, 2],
v = [{'a':1, 'b':2}, {'a':3}, {'b':4}])
which looks like this:
k v
▪▪▪▪ ▪▪▪▪▪▪▪▪
1 {'a': 1, 'b': 2}
1 {'a': 3}
2 {'b': 4}
What I'm trying to do is to 1) group by k, and 2) aggregate the count in the dictionary.
The desired output:
k v
▪▪▪▪ ▪▪▪▪▪▪▪▪
1 {'a': 4, 'b': 2}
2 {'b': 4}
Is it possible to achieve with the latest pydatatable(v0.11)?
If you have a large dataset then consider expanding all dictionaries into a frame:
>>> DT = dt.cbind(dt.Frame(_key=[1,1,2]),
dt.Frame([{'a':1, 'b':2}, {'a':3}, {'b':4}]))
>>> DT
| _key a b
-- + ---- -- --
0 | 1 1 2
1 | 1 3 NA
2 | 2 NA 4
[3 rows x 3 columns]
After this, grouping is easy:
>>> from datatable import sum, f, by
>>> DT[:, sum(f[:]), by(f._key)]
| _key a b
-- + ---- -- --
0 | 1 4 2
1 | 2 0 4
[2 rows x 3 columns]