Frequência anual da superfície de água

/**
 * Water surface frequency using MapBiomas Water data (binary: 1 = water).
 */

var asset = 'projects/mapbiomas-public/assets/brazil/water/collection5/mapbiomas_brazil_collection5_water_annual_v4';

// --- Parameters --- Adapt if needed
var startYear = 1985;   // First year of analysis (min: 1985)
var endYear = 2025;     // Last year of analysis (max: 2025)

var targetClass = 1;    // 1 = water surface
var bandPrefix = 'classification_';

// Light blue -> dark blue gradient
var palette = ['#ADD8E6', '#00008B'];

var image = ee.Image(asset);

/**
 * Counts how many times the target class appeared in the selected period.
 * @param {ee.Image} image - Multi-band image (one band per year).
 * @param {number} targetClass - Class value to count.
 * @param {number} startYear - First year of the period.
 * @param {number} endYear - Last year of the period.
 * @param {string} bandPrefix - Prefix of the band names.
 * @returns {ee.Image} - Image with the number of occurrences (0 masked out).
 */
var getClassFrequency = function (image, targetClass, startYear, endYear, bandPrefix) {
  var bands = ee.List.sequence(startYear, endYear).map(function (year) {
    return ee.String(bandPrefix).cat(ee.Number(year).format('%.0f'));
  });

  return image.select(bands)
    .eq(targetClass)
    .reduce(ee.Reducer.sum())
    .selfMask();
};

// --- Visualization ---
var nYears = endYear - startYear + 1;
var frequencies = getClassFrequency(image, targetClass, startYear, endYear, bandPrefix);

Map.centerObject(image, 4);
Map.addLayer(frequencies, {min: 1, max: nYears, palette: palette},
  'Water frequency ' + startYear + '-' + endYear);