Aggregate GPM hourly data to daily in GEE - google-app-engine

Question

I need to aggregate the sum of 48 half-hourly images per day of a GPM collection getting an imageCollection with the band "precipitationCal" and daily images
I've tried to fill and iterate an empty featureCollection but I get an empty collection without images
var dataset = ee.ImageCollection('NASA/GPM_L3/IMERG_V05')
var startdate = ee.Date.fromYMD(2014,3,1)
var enddate = ee.Date.fromYMD(2014,4,1)
var precipitation = dataset.filter(ee.Filter.date(startdate,enddate)).select('precipitationCal')
print(precipitation)
var difdate = enddate.difference(startdate, 'day')
// Time lapse
var lapse = ee.List.sequence(0, difdate.subtract(1))
var startdate = ee.Date('2014-01-01')
var listdates = lapse.map(function(day){
return startdate.advance(day, 'day')
})
var pts = ee.FeatureCollection(ee.List([]))
var newft = ee.FeatureCollection(listdates.iterate(function(img, ft) {
// Cast
ft = ee.FeatureCollection(ft)
var day = ee.Date(img)
// Filter the collection in one day
var day_collection = precipitation.filterDate(day, day.advance(1, 'day'))
// Get the sum of all 24 images into one Image
var sum = ee.Image(day_collection.sum())
// Return the FeatureCollection with the new properties set
return sum
}, listdates))

Answer 1

Please have a try about my package pkg_trend. aggregate_prob function in it, works just like aggregate in R language.
var imgcol_all = ee.ImageCollection('NASA/GPM_L3/IMERG_V06');
function add_date(img){
var date = ee.Date(img.get('system:time_start'));
var date_daily = date.format('YYYY-MM-dd');
return img.set('date_daily', date_daily);
}
var startdate = ee.Date.fromYMD(2014,3,1);
var enddate = ee.Date.fromYMD(2014,4,1);
var imgcol = imgcol_all
.filter(ee.Filter.date(startdate,enddate)).select('precipitationCal')
.map(add_date);
// imgcol = pkg_trend.imgcol_addSeasonProb(imgcol);
print(imgcol.limit(3), imgcol.size());
var pkgs = require('users/kongdd/pkgs:pkgs.js');
var imgcol_daily = pkgs.aggregate_prop(imgcol, "date_daily", 'sum');
print(imgcol_daily);
Map.addLayer(imgcol_daily, {}, 'precp daily');
The GEE link is https://code.earthengine.google.com/3d8c7e68e0a7a16554ff8081880bfdad

Answer 2

According to GEE GPM page, This product is a half-hour precipitation rate. So, to get daily sum with the code above you should divide every image in collection by 2.