gusucode.com > demos工具箱matlab源码程序 > demos/meanArrivalDelayByDayMapper.m
function meanArrivalDelayByDayMapper(data, ~, intermKVStore) % Mapper function for the MeanByGroupMapReduceExample. % Copyright 2014 The MathWorks, Inc. % Data is an n-by-2 table: first column is the DayOfWeek and the second % is the ArrDelay. Remove missing values first. delays = data.ArrDelay; day = data.DayOfWeek; notNaN =~isnan(delays); day = day(notNaN); delays = delays(notNaN); % find the unique days in this chunk [intermKeys,~,idx] = unique(day, 'stable'); % group delays by idx and apply @grpstatsfun function to each group intermVals = accumarray(idx,delays,size(intermKeys),@countsum); addmulti(intermKVStore,intermKeys,intermVals); function out = countsum(x) n = length(x); % count s = sum(x); % mean out = {[n, s]};