set-operations

问题 Python 2.7, numpy, create levels in the form of a list of factors. I have a data file which list independent variables, the last column indicates the class. For example: 2.34,4.23,0.001, ... ,56.44,2.0,"cloudy with a chance of rain" Using numpy, I read all the numeric columns into a matrix, and the last column into an array which I call "classes". In fact, I don't know the class names in advance, so I do not want to use a dictionary. I also do not want to use Pandas. Here is an example of the

问题 I had seen this test question on Pluralsight: Given these sets: x = {'a', 'b', 'c', 'd'} y = {'c', 'e', 'f'} z = {'a', 'g', 'h', 'i'} What is the value of x | y ^ z ? The expected answer is: {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i'} Combines the sets (automatically discarding duplicates), and orders them from lowest to greatest. My questions are: What is this expression called? Why do I get 3 different results from 3 different Python versions? Result on Python 3.7.5 on Ubuntu 18.04: {'c',

问题 I had seen this test question on Pluralsight: Given these sets: x = {'a', 'b', 'c', 'd'} y = {'c', 'e', 'f'} z = {'a', 'g', 'h', 'i'} What is the value of x | y ^ z ? The expected answer is: {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i'} Combines the sets (automatically discarding duplicates), and orders them from lowest to greatest. My questions are: What is this expression called? Why do I get 3 different results from 3 different Python versions? Result on Python 3.7.5 on Ubuntu 18.04: {'c',

问题 In CMake, lists are used extensively. Sometimes you have two lists of items (strings, basically), and you want to consider their intersection, difference or union. Like in this case that just came up for me. How do I produce such intersection, difference or union lists? Note: The outputs need to have no duplicates, the inputs not really 回答1: Suppose our lists are in variables S and T . For the union, write: list(APPEND union_list ${S} ${T}) list(REMOVE_DUPLICATES union_list) For set

问题 In CMake, lists are used extensively. Sometimes you have two lists of items (strings, basically), and you want to consider their intersection, difference or union. Like in this case that just came up for me. How do I produce such intersection, difference or union lists? Note: The outputs need to have no duplicates, the inputs not really 回答1: Suppose our lists are in variables S and T . For the union, write: list(APPEND union_list ${S} ${T}) list(REMOVE_DUPLICATES union_list) For set

问题 I assume there's no good way to do so, but if you had to, how would you implement set operations on Appengine's datastore? For example given two collections of integers, how would you store them in the datastore to get a good performance for intersect and except (all those items in A that are not in B) operations? 回答1: There aren't any built in set operations in the datastore API. I see you having two options: For smallish sets (hundreds of items) You might get away with doing keys-only

问题 Are there any standard library calls I can use to either perform set operations on two arrays, or implement such logic myself (ideally as functionally and also efficiently as possible)? 回答1: Yes, Swift has the Set class. let array1 = ["a", "b", "c"] let array2 = ["a", "b", "d"] let set1:Set<String> = Set(array1) let set2:Set<String> = Set(array2) Swift 3.0+ can do operations on sets as: firstSet.union(secondSet)// Union of two sets firstSet.intersection(secondSet)// Intersection of two sets

问题 Are there any standard library calls I can use to either perform set operations on two arrays, or implement such logic myself (ideally as functionally and also efficiently as possible)? 回答1: Yes, Swift has the Set class. let array1 = ["a", "b", "c"] let array2 = ["a", "b", "d"] let set1:Set<String> = Set(array1) let set2:Set<String> = Set(array2) Swift 3.0+ can do operations on sets as: firstSet.union(secondSet)// Union of two sets firstSet.intersection(secondSet)// Intersection of two sets

问题 I have the following tables: work_units - self explanatory workers - self explanatory skills - every work unit requires a number of skills if you want to work on it. Every worker is proficient in a number of skills. work_units_skills - join table workers_skills - join table A worker can request the next appropriate free highest priority (whatever that means) unit of work to be assigned to her. Currently I have: SELECT work_units.* FROM work_units -- some joins WHERE NOT EXISTS ( SELECT skill

问题 I want to write a C++ class that offers set operations that work on vectors of strings and vectors of my own data type. Are there any easy ways of doing this rather than writing a different function for each data type? So far I have written operations for string vectors. Below shows an example of my set union: vector<string> SetOperations::set_union(vector<string> set1, vector<string> set2) { for(std::vector<int>::size_type i = 0; i < set1.size(); i++) { set1.push_back(set2.at(i)); } return