Create function for filtering date by quarter in Google Earth Engine

Question

I'm trying to figure out a function to filter image by quarter (January - March, Arpil - July, etc) of Landsat Image Collection to calculate NDVI for each three-month period between 2013 and 2018. My purpose is to adjust the code this link https://code.earthengine.google.com/f590c95bd17454789cde0eb8d1be4850 to compute NDVI in quarter instead of five-year period.

I am planning to add this code below, however i don't know exactly it could be possible or not.

var start = ee.Date('01-01-2013');
var end = ee.Date('31-03-2013');
var date_range = ee.DateRange(start,end);
var fnc = function(d1) {
  var S1 = ee.ImageCollection("LANDSAT/LC08/C01/T1_SR")
    .filterDate(date_range)
    .filterBounds(table)
  return(S1.first())
}
var quarter1 = ee.ImageCollection(dates.map(fnc));
print(mt)

Answer 1

There are multiple ways to make these composite image. Note that you will have to choose a manner to reduce multiple images within the three-month date range to one image. .first() is generally a bad choice. I would recommend .median() for simple composites:

// get start and end date and define the number of quarterly composites
var start = ee.Date('2013-01-01');
var end = ee.Date('2019-01-01');
var numbQuarters = end.difference(start, 'month').divide(3).ceil();

// make a composite image for every quarter
var quarterlyImages = ee.ImageCollection.fromImages(
            ee.List.sequence(1, numbQuarters).map(function(quarter){
              var startTemp = start.advance(
                              ee.Number(quarter).subtract(1).multiply(3), 'month');
              var endTemp = start.advance(ee.Number(quarter).multiply(3), 'month');
              var image = ee.ImageCollection("LANDSAT/LC08/C01/T1_SR")
                                .filterDate(startTemp, endTemp)
                                .filterBounds(geometry)
                                // define a way to composite an image
                                .median(); // .mean(); .mosaic(); .max(); etc

              return image.set('system:time_start', startTemp.millis(),
                               'system:time_end', endTemp.millis());
            }));

Link code

Answer 2

I'm trying to use .clip(table) function to cut the table polygon however it's not working (quarterlyImages.clip is not a function). Could you please tell me how to adjust the code ?

"print('image collection', quarterlyImages)
print('startDates', quarterlyImages.aggregate_array('system:time_start'))
print('sendDates', quarterlyImages.aggregate_array('system:time_end'))
Map.addLayer(quarterlyImages.clip(table),{ min:0, max: 3500, bands: 'B6, B5, B4'});
Map.centerObject(table, 7);

https://code.earthengine.google.com/9cf431a559131a62d54c7d4977559e9e