reduce

问题 I have a data frame containing a time series with two time stamp columns, d$day and d$time , and say, for simplicity, one measured variable d$val1 . Suppose I want to examine the situation at the close of each day's experiment, i.e. the last measurement, if it exists. (Not every day has a measurement, and measurements can be taken at different times each day.) I would like to be able to aggregate by day and use some sort of last() or tail() function on time to pull back the corresponding val

问题 In MPI, I am doing a reduce operation(minimum) on a value. This works fine, but how do I grab the processor number that the minimum came from and solicit that processor for more information(or send the additional data with the reduce operation)? 回答1: If you don't mind paring each value locally with an integer index (filled in this case with the value of the local rank), you can use the MPI_MINLOC or MPI_MAXLOC builtin operations for reduce; or it's fairly easy to write your own MPI reduction

问题 I proceed java 8 learning. I have found interesting behaviour: lets see code sample: // identity value and accumulator and combiner Integer summaryAge = Person.getPersons().stream() //.parallel() //will return surprising result .reduce(1, (intermediateResult, p) -> intermediateResult + p.age, (ir1, ir2) -> ir1 + ir2); System.out.println(summaryAge); and model class: public class Person { String name; Integer age; ///... public static Collection<Person> getPersons() { List<Person> persons =

问题 I'm trying to learn JS and I have some questions about reduce() I want to know how can I know what parameters this function needs and how I should call them. are this parameters connected with any data or the array outside the function. or this parameters propose is only to be available in this local context of the callback to work as const and be able to store some date for the correct execution of the .reduce() . Thank You For Your Time Just trying to understand .reduce() const companies= [

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 3 years ago . var ｙ= '110001'.split("").reverse(); var sum = 0; for (var i = 0; i < y.length; i++) { sum += (y[i] * Math.pow(2, i)); } console.log(sum); 回答1: It would be simplest to do console.log(Array.from('110001').reduce((prev, cur) => prev << 1 | cur)); << is the left-bitshift operator, which here

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 3 years ago . var ｙ= '110001'.split("").reverse(); var sum = 0; for (var i = 0; i < y.length; i++) { sum += (y[i] * Math.pow(2, i)); } console.log(sum); 回答1: It would be simplest to do console.log(Array.from('110001').reduce((prev, cur) => prev << 1 | cur)); << is the left-bitshift operator, which here

问题 I am sure there is a clean way to do this, but I have no idea how to do it. I want to pluck a column out such that I am only returning the first occurrence of a value, but I want to keep the key that went with it. I have a dataset that I want reduced. I want to pluck out the 'precip'. Say I have this: [ "2019-01-01" => {"temp" : "cold", "season" : "winter", "precip" : "snow"}, "2019-02-01" => {"temp" : "cold", "season" : "winter", "precip" : "none"}, "2019-03-01" => {"temp" : "mild", "season"

问题 So I recently noticed that the order of you put in parameters in ruby's reduce method influenced the results. a = ["1", "2", "3"] a.reduce {|val, con| val + con} a = ["123"] However a.reduce {|val, con| con + val} a = ["321"] I think it only matters how you give order to |val, con| pair, which means if con shows at the latter position, the result of every step is always gonna be stored in con. And these two should yield the same result. But obviously not here. Anyone could provide some tips?

问题 I was trying to analyse the default map reduce job, that doesn't define a mapper or a reducer. i.e. one that uses IdentityMapper & IdentityReducer To make myself clear I just wrote my identity reducer public static class MyIdentityReducer extends MapReduceBase implements Reducer<Text,Text,Text,Text> { @Override public void reduce(Text key, Iterator<Text> values, OutputCollector<Text, Text> output, Reporter reporter) throws IOException { while(values.hasNext()) { Text value = values.next();

问题 I'm new at android devolpment, so I am developing an alphabet app for an old language, the app would look like this first page has a picture and two buttons first button links to a page with text second button links to a page with 24 images (alphabets), if you click on one of the image (alphabet) then you move on to a page with picture (alphabet) and below the picture there is a button to listen to the pronunciation of the letter in the end the app will contain 50 images , 24 audio files and