I have successfully extracted distance to nearest human settlement with rgee function fastDistanceTransform, where the original layer is a single image (DLR/WSF/WSF2015/v1). I want to repeat this with distance to nearest road, but the road dataset is a featureCollection and not an image.
I have successfully converted to image in the gee code editor with:
var dataset = ee.FeatureCollection('TIGER/2016/Roads')
.map(function(feature){
var num = ee.Number.parse(feature.get('linearid'));
return feature.set('linearid', num);
});
var roads = dataset
.reduceToImage({
properties: ['linearid'],
reducer: ee.Reducer.first()
});
Map.setCenter(-99.976, 40.38, 5);
Map.addLayer(roads, {
});
But I cannot get it to repeat the same in the R package rgee. I am using code:
road = ee$FeatureCollection("TIGER/2016/Roads")$
map(function(feature) { num = ee$Number$parse(feature$get('linearid'))
return(feature$set('linearid', num)) })
road2 = road$reduceToImage(properties=road$select('linearid'), reducer=ee$Reducer$first())
Map$addLayer(road2, {}, "road2")
But I get the error:
Error in py_call_impl(callable, dots$args, dots$keywords) :
ee.ee_exception.EEException: Collection.reduceToImage, argument 'properties': Invalid type.
Expected type: List<String>.
Actual type: FeatureCollection.
Can anyone help me fix this error so I can continue using 'road2' as an image? I think it has something to do with this (https://github.com/r-spatial/rgee/issues/232) "It seems that passing an ee.Image object in Javascript immediately changes it to a List"
I don't know the R language, but it looks like you made a mistake in your translation.
var roads = dataset
.reduceToImage({
properties: ['linearid'],
reducer: ee.Reducer.first()
});
Here the properties argument to reduceToImage is a list of strings.
road2 = road$reduceToImage(properties=road$select('linearid'), reducer=ee$Reducer$first())
Here you are not constructing a list, but instead calling road$select. So, the result is an image, not the list of strings that reduceToImage wants.
Maybe you want properties=list('linearid') ? Again, I don't know R or rgee, so I can't say whether this is correct.