Suppose the bottom left coordinates and the upper right coordinates are respectively [0, 0] and [100, 100]. From MongoDB 3.2 you can use the $slice operator to return a subset of an array which is what you want. db.collection.aggregate([ { “$match”: { “loc”: { “$geoWithin”: { “$box”: [ [0, 0], [100, 100] ] } }} … Read more
itertools.groupby can do what you want: import itertools import operator L = [(‘grape’, 100), (‘grape’, 3), (‘apple’, 15), (‘apple’, 10), (‘apple’, 4), (‘banana’, 3)] def accumulate(l): it = itertools.groupby(l, operator.itemgetter(0)) for key, subiter in it: yield key, sum(item[1] for item in subiter) print(list(accumulate(L))) # [(‘grape’, 103), (‘apple’, 29), (‘banana’, 3)]
A very simple answer would be to sort by the GroupID, this will put those rows together in groups. However, I’m guessing you want a header row displayed before each group. You can provide an alternative <mat-row *matRowDef=”… that uses a where clause. This can be used to display a non-default set of columns. The … Read more
COUNT(expr) will count the number of rows where expr is not null, thus you can count the number of nulls with expressions like these: SELECT count(a) nb_a_not_null, count(b) nb_b_not_null, count(*) – count(a) nb_a_null, count(*) – count(b) nb_b_null, count(case when a is not null and b is not null then 1 end)nb_a_b_not_null count(case when a is … Read more
The fundamental question here is how to project a DateTime instance into a week of year value. This can be done using by calling Calendar.GetWeekOfYear. So define the projection: Func<DateTime, int> weekProjector = d => CultureInfo.CurrentCulture.Calendar.GetWeekOfYear( d, CalendarWeekRule.FirstFourDayWeek, DayOfWeek.Sunday); You can configure exactly how the “week number” is determined by tweaking the parameters in the … Read more
What you need is the $cond operator of aggregation framework. One way to get what you want would be: db.foo.aggregate([ { $project: { item: 1, lessThan10: { // Set to 1 if value < 10 $cond: [ { $lt: [“$value”, 10 ] }, 1, 0] }, moreThan10: { // Set to 1 if value > … Read more
I figured out the answer. This seems to work: from sklearn.model_selection import GroupShuffleSplit splitter = GroupShuffleSplit(test_size=.20, n_splits=2, random_state = 7) split = splitter.split(df, groups=df[‘Group_Id’]) train_inds, test_inds = next(split) train = df.iloc[train_inds] test = df.iloc[test_inds]
var arr = [ ‘Car’, ‘Car’, ‘Truck’, ‘Boat’, ‘Truck’ ]; var hist = {}; arr.map( function (a) { if (a in hist) hist[a] ++; else hist[a] = 1; } ); console.log(hist); results in { Car: 2, Truck: 2, Boat: 1 } This works, too: hist = arr.reduce( function (prev, item) { if ( item in … Read more
Firstly, for those who haven’t already read up on the subject: Using GROUP BY with ROLLUP, CUBE, and GROUPING SETS That being said, don’t think about these grouping options as ways to get a result set. These are performance tools. Let’s take ROLLUP as a simple example. I can use the following query to get … Read more