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I have a code that suppose to count number of pixels in a polygon and to add it to the polygon as a dictionary. First NDVI calculted and then differrent ranges inside the polygon should be calculte: the percent of NDVI pixels that their value is higher than 0.2, between 0.2-0.4, between 0.4-0.6 ect.... My problem is that my test polygon doesn't have all the values inside it and for that reason I get the next error message:

Collection.toList: The value of 'count' must be positive. Got: 0

How can I tell my code to still work/ ignor when he doesn't find match pixels?

This is link to my code: https://code.earthengine.google.com/ff24c08f6d3acd50a8108ca656da4b9f

This is the part where I create the ranges:

var stats = listOfImages.map(function(img){
  var image = ee.Image(img).select('NDVI_mean');


  var HighVeg = image.gt(0.6).selfMask().reduceRegion({
    reducer: ee.Reducer.count(),
    geometry: geometry,
    crs: 'EPSG:4326',
    //maxPixels:1310361348,
    scale: 20,
  }).values().get(0);

  var LowModerate = image.gt(0.2).and(image.lt(0.4)).selfMask().reduceRegion({
    reducer: ee.Reducer.count(),
    geometry: geometry,
    crs: 'EPSG:4326',
    //maxPixels:1310361348,
    scale: 20,
  }).values().get(0);

  var ModHigh = image.gt(0.4).and(image.lt(0.6)).selfMask().reduceRegion({
    reducer: ee.Reducer.count(),
    geometry: geometry,
    crs: 'EPSG:4326',
    //maxPixels:1310361348,
    scale: 20,
  }).values().get(0);

    var low = image.lt(0.2).selfMask().reduceRegion({
    reducer: ee.Reducer.count(),
    geometry: geometry,
    crs: 'EPSG:4326',
    //maxPixels:1310361348,
    scale: 20,
  }).values().get(0);

    var total = image.gt(-1).selfMask().reduceRegion({
    reducer: ee.Reducer.count(),
    geometry: geometry,
    crs: 'EPSG:4326',
    //maxPixels:1310361348,
    scale: 20,
  }).values().get(0);

  return image.set('HighVeg', HighVeg).set('LowModerate', LowModerate).set('ModHigh', ModHigh).set('low', low).set('total', total);
});

1 Answer 1

3

The answer is in your script.

When you print your collection size it says there is 0 images in there. Change the filter parameters you apply in your script to ensure there is actually images in your collection

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