reduce

问题 I am trying to use a Promise.all inside of a reduce and cannot get my function to work, unless there is only one user in my array. The starting object of the reduce is a Promise . The first time through the reduce , the Promise has .all available on it. The second time through, the .all is not available. return UserQueries.addUsersOnCasefileCreate(input).then(users => { return users.reduce((promise, user) => { return promise.all([ AddressQueries.addAddress(user.address, user.userId, input

问题 I'm trying to recreate the reduce method but as the original function. This helped me to understand a lot but I have one little issue: How to re-create Underscore.js _.reduce method? When I plug in arrays it works right, but objects don't work. I get undefined. I would appreciate advice on what I should change. I commented where I think I should change something but I'm confused exactly what I need to change it to. I also created my own each function. You can find my code here: http://goo.gl

问题 I have an RDD: JavaRDD<Tuple2<Tuple2<String, Long>, Long>> mappedRdd = dataRDD .values().map(mapFunc); I want to run a reduce function on it: private static Function2<Tuple2<Tuple2<String, Long>, Long>, Tuple2<Tuple2<String, Long>, Long>, Tuple2<Tuple2<String, Long>, Long>> redFunc2 = new Function2<Tuple2<Tuple2<String, Long>, Long>, Tuple2<Tuple2<String, Long>, Long>, Tuple2<Tuple2<String, Long>, Long>>() { @Override public Tuple2<String, MetricDatum> call( Tuple2<Tuple2<String, Long>, Long>

问题 Can someone explain the structure of reduce() in the following example: def f2(list): return reduce(lambda string, item: string + chr(item), list, "") I know that f2 converts a list of int's into a string, but my problem is understanding reduce in this context. I know the basic structure of reduce is reduce(function, sequence[, initial]) but this is somehow confusing to me. Can someone explain reduce(lambda string, item: string + chr(item), list, "") and give me some similar examples ? Thanks

问题 My map task completes successfully and I can see the application logs, but reducer stays in pending state Kind % Complete Num Tasks Pending Running Complete Killed Failed/Killed Task Attempts map 100.00% 200 0 0 200 0 0 / 40 reduce 0.00% 1 1 0 0 0 0 / 0 When I look at reduce task, I see All Task Attempts No Task Attempts found When I see the hadoop-hduser-jobtracker-master.log, I see the following : 2011-10-31 00:00:00,238 WARN org.apache.hadoop.mapred.JobInProgress: No room for reduce task.

问题 (K1, (v1, v2)) (K2, (v3, v4)) (K1, (v1, v5)) (K2, (v3, v6)) How can I sum up the values of the key provided the first value is the some or eque such that I get (k1, (v1,v2+v5), (k2,(v3,v4+v6) ? 回答1: IIUC, you need to change the key before the reduce , and then map your values back in the desired format. You should be able to do the following: new_rdd = rdd.map(lambda row: ((row[0], row[1][0]), row[1][1]))\ .reduceByKey(sum). .map(lambda row: (row[0][0], (row[0][1], row[1]))) 来源： https:/

问题 I'm reading in an array from a JSON file because I need to perform a reduce on it before turning it into a DataFrame for further manipulation. For the sake of argument, let's say this is it a = [Dict("A" => 1, "B" => 1, "C" => "a") Dict("A" => 1, "B" => 2, "C" => "b") Dict("A" => 2, "B" => 1, "C" => "b") Dict("A" => 2, "B" => 2, "C" => "a")] Now, the reduce I'm performing would be greatly simplified if I could group the array by one or more keys (say, A and C), perform a simpler reduce on

问题 Hello I want to transform array to object input = [1,2,3] expected output = {1:1,2:2,3:3} I tried this const arrToObj = (arr) => { arr.reduce((acc, curr, i, arr)=> { acc[curr]=arr[i] },{}) } console.log(arrToObj([1,2,3,4,5,6,7,8,9])) but it throws errror in second iteration. What is wrong and how to make it work? 回答1: What you have tried so far has two problems The first is serious: You forgot to return from your accumulating function, so it returns undefined . It throws the second time

问题 I’m looking to apply a function over an initial dataframe multiple times. As a simple example, take this data: library(dplyr) thisdata <- data.frame(vara = seq(from = 1, to = 20, by = 1) ,varb = seq(from = 1, to = 20, by = 1)) And here is a simple function I would like to run over it: simplefunc <- function(data) {datasetfinal2 <- data %>% mutate(varb = varb+1) return(datasetfinal2)} thisdata2 <- simplefunc(thisdata) thisdata3 <- simplefunc(thisdata2) So, how would I run this function, say 10

问题 OK this question was put on hold for the following reason; "This question was caused by a problem that can no longer be reproduced or a simple typographical error. " I just would like to confirm that the problem still exists as of now on stackoverflow sandbox, repl.it sanbox and even on firefox console and it is certainly not a typo. Copy paste the code to Firefox console and it will not work as it should. I have been trying to sort several objects in a Map object according to one specific