google-earth-engine – Using Variable for Property Name in Google Earth Engine ee.Feature

google-earth-enginegoogle-earth-engine-javascript-apisyntaxerror

I would like to know if it is possible to set a property name using a computed variable in GEE.

For example, I create the following feature:

var feature = ee.Feature(null,{propertyName: 0.85});

and would like to be able to use a property name which was previously defined, so instead of using "propertyName" I would use var propertyName = 'propertyValue' .

I found this Stack Overflow answer relating to JavaScript in general which states that you may place the variable name in between brackets.

var foo = "bar";
var ob  = { [foo]: "something" }; // ob.bar === "something"

However trying the same notation in GEE only produced an error SyntaxError: Unexpected token.

Best Answer

var feature = ee.Feature(null).set(propertyName, 0.85);

This will also work if propertyName Earth Engine computed/server-side string values, not just JavaScript strings.

Related Solutions

Google Earth Engine – Adding Property to ee.Feature Based on Another Property

A general rule for this kind of problem is to express your repetitive structure as data, not code. A mapping from one value to another is a kind of data that can be stored in a dictionary.

So, first define a dictionary. (This can be done more cleverly to not have to list the numbers explicitly, but let's keep things simple.)

var taxOrders = ee.Dictionary({
  'Alfisols': 1,
  'Andisols': 2,
  'Aridisols': 3,
  'Entisols': 4,
  'Gelisols': 5,
  'Histosols': 6,
  'Inceptisols': 7,
  'Mollisols': 8,
  'Oxisols': 9,
  'Spodosols': 10,
  'Ultisols': 11,
  'Vertisols': 12,
});

Then, use that dictionary inside the feature mapping function.

var addTaxOrderNum = function(feature) {
  var taxOrderNum = taxOrders.get(feature.get('TaxOrder'));
  return feature.set('taxOrderNum', taxOrderNum);
};

https://code.earthengine.google.com/423c5b4f30b3928c57b8ec9413912bf2

Google Earth Engine – How to Export Tables with Variable Name in Google Earth Engine

You've already extracted all the data from Earth Engine using the evaluate function, so you can no longer use Earth Engine functions on the results. The feature you have inside the function is going to have a properties dictionary in it, and the variable you're trying to access will be inside that. So you'd access it with something like this instead of using get():

feature['properties']['grdc_no']

But you won't then be able to export the results, since they're in your browser and no longer in Earth Engine.

If the bigger picture of what you're trying to do is to export each feature to its own file, then I think it would be easier to just split them up once you've downloaded all of them.

Best Answer

Related Solutions

Google Earth Engine – Adding Property to ee.Feature Based on Another Property

Google Earth Engine – How to Export Tables with Variable Name in Google Earth Engine

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