I would like to create annual Landsat frequency maps. So the purpose would be to see, what is the percentage of occurrence of index 1

  1. I would like to count all images per year
  2. I would like to count images where the index values equal 1 (per year)
  3. Finally, create annual maps which show (question2/question1)*100 per pixel

I know how to create an annual reduce mean function, but I don't know how to add multiple reduce functions inside it if it is necessary.

var yearly= ee.ImageCollection.fromImages(
    years.map(function(y) {
      return collection 
        .filter(ee.Filter.calendarRange(y, y, 'year'))
        .set('year', y)

1 Answer 1


Without seeing your reducer, it's hard to offer any concrete solution, but a general sketch is: you map a function to apply whatever transformations you need to your images (e.g. thresholding), then apply a combined reducer.

  • Thank you! That I was looking for!
    – AveAT
    Mar 2, 2023 at 11:43

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