aggregation

问题 I looked for documentation of how to perform $out in an aggregation but I didn't find. This is my query: Top.aggregate([ {$sort: {created: -1}}, {$group: {_id:'$location', title:{$push: '$title'}}}, {$project: {location: '$location', mostRecentTitle: '$title'}}, {$out: "aggr_out"} ]).exec(function(err, docs) { console.log(docs); console.log(err) }); Schema: var schema = mongoose.Schema({ location: {type: String}, title: {type: String}, created: {type: Number, default: Math.floor(new Date() /

问题 I have a MultivaluedMap and a list of strings, and I would like to see which of those string are keys in the MultivaluedMap . For each of the strings that are keys in the MultivaluedMap , I want to construct a new Thing out of the value of that key, set that string as a new key in a new HashMap<String, Thing> , and set the new Thing I've created as the value for that new key in the HashMap . Right now, using a vanilla forEach , I have the following working solution: MultivaluedMap<String,

问题 I have a dataset in R of student weekly allowances by class, which looks like: Year ID Class Allowance 2013 123 Freshman 100 2013 234 Freshman 110 2013 345 Sophomore 150 2013 456 Sophomore 200 2013 567 Junior 250 2014 678 Junior 100 2014 789 Junior 230 2014 890 Freshman 110 2014 891 Freshman 250 2014 892 Sophomore 220 How can I summarize the results by group (Year/Class) to get sum and % (by group)? Getting sum seems easy with ddply by just couldn't get the % by group part right. It works for

问题 I am preparing for my programming exam and came across this question, I know that in aggregation the object is borrowed, and in composition the object is owned. Is the answer composition? Is an ArrayList<X> an aggregation of X or composition of X ? ArrayList<Point> pts = new ArrayList<Point>(); Point p = new Point(0., 0., 0.); pts.add(p); p.setX( 10.0 ); System.out.println(p); System.out.println(pts.get(0)); 回答1: From here: Simple rules: A "owns" B = Composition : B has no meaning or purpose

问题 I am preparing for my programming exam and came across this question, I know that in aggregation the object is borrowed, and in composition the object is owned. Is the answer composition? Is an ArrayList<X> an aggregation of X or composition of X ? ArrayList<Point> pts = new ArrayList<Point>(); Point p = new Point(0., 0., 0.); pts.add(p); p.setX( 10.0 ); System.out.println(p); System.out.println(pts.get(0)); 回答1: From here: Simple rules: A "owns" B = Composition : B has no meaning or purpose

问题 I'm studying the GoF design patterns, in particular the Facade pattern. I understand its use and implementation, but I have a doubt about its UML model. The solution proposed by my professor, summarized, is the following: public class Facade{ private ClassA c1; private ClassB c2; private ClassC c3; public Facade(){ this.c1 = new ClassA; this.c2 = new ClassB; this.c3 = new ClassC; } public void FacadeMethod(){ ... c1.operationA(); c2.operationB(); c3.operationC(); ... } } The UML model

问题 This is my transaction data data id from to date amount <int> <fctr> <fctr> <date> <dbl> 19521 6644 6934 2005-01-01 700.0 19524 6753 8456 2005-01-01 600.0 19523 9242 9333 2005-01-01 1000.0 … … … … … 1055597 9866 9736 2010-12-31 278.9 1053519 9868 8644 2010-12-31 242.8 1052790 9869 8399 2010-12-31 372.2 Now for each distinct account in from column, I want to keep track of how much transaction amount they sent over last 6 month at the time the transaction was made and so I want to do it

问题 This is my transaction data data id from to date amount <int> <fctr> <fctr> <date> <dbl> 19521 6644 6934 2005-01-01 700.0 19524 6753 8456 2005-01-01 600.0 19523 9242 9333 2005-01-01 1000.0 … … … … … 1055597 9866 9736 2010-12-31 278.9 1053519 9868 8644 2010-12-31 242.8 1052790 9869 8399 2010-12-31 372.2 Now for each distinct account in from column, I want to keep track of how much transaction amount they sent over last 6 month at the time the transaction was made and so I want to do it

问题 I often need to aggregate a sequence of nodes using XSLT 1.0 but I always struggle to find a clean solution. This is a typical example; Input <x>Foo/Red</x> <x>Foo/Green</x> <x>Foo/Blue</x> <x>Bar/Hello</x> <x>Bar/World</x> Desired output <y s="Foo">Red, Green, Blue</y> <y s="Bar">Hello, World</y> I always end up in a mess with this type of problem. Is there an elegant XSLT 1.0 solution to the above? I'm using PHP 's libxslt so I do have the exslt:node-set() function available to use if

问题 I have a dataframe in a format such as the following: Index Name Fruit Quantity 0 John Apple Red 10 1 John Apple Green 5 2 John Orange Cali 12 3 Jane Apple Red 10 4 Jane Apple Green 5 5 Jane Orange Cali 18 6 Jane Orange Spain 2 I need to turn it into a dataframe such as this: Index Name All Fruits Apples Total Oranges Total 0 John Apple Red, Apple Green, Orange Cali 15 12 1 Jane Apple Red, Apple Green, Orange Cali, Orange Spain 15 20 Question is how do I do this? I have looked at the groupby