2

I have a dictionary of % landcover from the 2016 NLCD. I am having trouble trying to make a bar chart to show the percentage of each land cover class in a given area (DEM vector). The dictionary is an object w/ 15 properties - I want the data in this object to be used for a bar chart.

///////////Load Landcover dataset////////////
var dataset = ee.Image('USGS/NLCD/NLCD2016')
  .clip(aoi) ;
print(dataset);
var landcover = dataset.select('landcover');
var landcoverVis = {
  min: 0.0,
  max: 95.0,
  palette: [
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '466b9f',
    'd1def8',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    'dec5c5',
    'd99282',
    'eb0000',
    'ab0000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    'b3ac9f',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '68ab5f',
    '1c5f2c',
    'b5c58f',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    'af963c',
    'ccb879',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    'dfdfc2',
    'd1d182',
    'a3cc51',
    '82ba9e',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    'dcd939',
    'ab6c28',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    '000000',
    'b8d9eb',
    '000000',
    '000000',
    '000000',
    '000000',
    '6c9fb8'
  ],
};

Map.addLayer(landcover, landcoverVis, 'Landcover');

//crop landcover by DEM_vector
var landcover_clip = landcover.clip(DEM_vector);
print(landcover_clip);

Map.addLayer(landcover_clip, {}, 'landcover_clip');

//Calculate percentage of landcover <5m
var frequency = landcover.reduceRegion({
  reducer:ee.Reducer.frequencyHistogram(),
  maxPixels:2e9,
  geometry:DEM_vector
});
print('Pixel frequency', frequency);

//turn frequency into percentage
var dict = ee.Dictionary(frequency.get('landcover'));
var sum = ee.Array(dict.values()).reduce(ee.Reducer.sum(),[0]).get([0]);
var new_dict = dict.map(function(k,v) {
  return ee.Number(v).divide(sum).multiply(100);
});
print('Land Cover (%)',new_dict);

1 Answer 1

1

Maybe something like this?

var chart = ui.Chart.feature.byProperty(
  ee.Feature(null, new_dict)
)
print(chart)

https://code.earthengine.google.com/b7aeb5096103ba3fbb829af87ea0bfc9

2
  • wow im embarassed by how easy that was..lol thank you! Any idea on how to get landcover names instead of values on the xaxis?
    – Anna
    Apr 21, 2020 at 15:14
  • Nothing to be embarrassed about - docs about EE charts is not that clear. It's mostly trial-and-error for me. Getting labels requires some massaging of your dictionary: code.earthengine.google.com/2e8646c6f7d591171e7f9fd578af14a6 Apr 21, 2020 at 15:39

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