var image=ee.Image('LANDSAT/LC08/C01/T1_SR/LC08_169062_20180205');

//define parameters

var green = image.select('B3');
var swi = image.select('B6');
var mndwi = green.subtract(swi).divide(green.add(swi)).rename('MNDWI');

var mndwipara = {min: 0, max: 0.7, palette: ['white', 'blue']};


Map.addLayer(mndwi, mndwipara, 'MNDWI');


//apply threshold to select only positive pixels
var lake_mask= mndwi.gt(0);
Map.addLayer(lake_mask);


//classification attempt - scum
var scum=image.expression(
'(nir)*0 + (nir < 0.018)*1', {
'nir': image.select('B5'),
'red': image.select ('B4'),
'green': image.select('B3'),
});

//classification attempt - sediment
var sediment=image.expression(
'(nir)*0 + (nir > 0.018 && red > green && green/nir < 1.3 && red/green>
nir/red)*1', {
'nir': image.select('B5'),
'red': image.select ('B4'),
'green': image.select('B3'),
 });

//classification attempt - lowbiomass
var lowbiomass=image.expression(
'(nir)*0 + (nir > 0.018 && red < green && green > 0.065 && nir < red)*1', {
'nir': image.select('B5'),
'red': image.select ('B4'),
'green': image.select('B3'),
 });


//classification attempt-scum
var scum=image.expression(
'(nir)*0 + (nir > 0.018 && red < green && green > 0.065 && nir > red && nir/red > 4.07)*1', {
'nir': image.select('B5'),
'red': image.select ('B4'),
'green': image.select('B3'),
 });

//classifcation attempt bleached scum
var bleached_scum=image.expression(
'(nir)*0 + (nir > 0.018 && red > green && green/nir > 1.3 && green > 0.065)*1', {
'nir': image.select('B5'),
'red': image.select ('B4'),
'green': image.select('B3'),
});

//classification attempt - microphytobenthos
var microphytobenthos=image.expression(
'(nir)*0 + (nir > 0.018 && red > green && green/nir < 1.3 && red/green< nir/red)*1', {
'nir': image.select('B5'),
'red': image.select ('B4'),
'green': image.select('B3'),
 });

//classification attempt - highbiomass
var highbiomass=image.expression(
'(nir)*0 + (nir > 0.018 && red < green && green > 0.065 && nir > red && nir/red < 4.07)*1', {
 'nir': image.select('B5'),
 'red': image.select ('B4'),
'green': image.select('B3'),
 });

/*
lake = 1
scum = 2
bleached_scum = 3
microphytobenthos = 4
highbiomass = 5
sediment

*/


var lake_mask_ = ee.Image(1).mask(lake_mask).toInt();
var scum_ = ee.Image(2).mask(lake_mask.mask(scum)).toInt();
var bleached_scum_ =
ee.Image(3).mask(lake_mask.mask(bleached_scum)).toInt();
var microphytobenthos_ =
ee.Image(4).mask(lake_mask.mask(microphytobenthos)).toInt();
var biomass_ = ee.Image(5).mask(lake_mask.mask(highbiomass)).toInt();

 var test = ee.ImageCollection([lake_mask_,scum_,bleached_scum_,microphytobenthos_,biomass_,]);

 var test = test.reduce(ee.Reducer.max());

 print(test);
 Map.addLayer(test,{min: 1, max: 5, palette: ['0000FF',
 '1BCFFF','66ff33','F4FF0B','FA0007']},'Classification');