Mean per district - Google Earth Engine

Question

I am trying to calculate the temperature per district in Afghanistan with the following code. However, I receive the following error when trying to calculate the mean per district:

Unrecognized arguments (collection) to function: Image.reduceRegion(image, reducer, geometry, scale, crs, crsTransform, bestEffort, maxPixels, tileScale)

---

///Code

var region = ee.FeatureCollection('users/mm/countries')
.filterMetadata('COUNTRY', 'equals', 'Afghanistan');

var districts = ee.FeatureCollection('users/mm/AFG_districts')

var modisLSTday = ee.ImageCollection('MODIS/MOD11A2')
.select('LST_Day_1km');

var modLSTday = modisLSTday.map(function(img) {return img.multiply(0.02)
.subtract(273.15)
.copyProperties(img,['system:time_start','system:time_end']);});

var collectionday = ee.ImageCollection(modLSTday).filterDate('2014-01-01', '2015-01-01');

var clippedday = collectionday.mean().clip(region);

var clippedday_district =  clippedday.reduceRegion({
  collection: districts,
  reducer: ee.Reducer.mean(),
  scale: 400,
})

;

Answer 1

You need to change .reduceRegion to .reduceRegions if you want to extract the mean for multiple districts.

var clippedday_district =  clippedday.reduceRegions({
  collection: districts,
  reducer: ee.Reducer.mean(),
  scale: 400,
})