I'm using reduceRegion to sum the number of water pixels determined by an NDWI. I want to do this on a collection of images to see change in water area over a period time.
The values are returned from the reduceRegion in the console and appear to be integers, but I am unable to extract them as such. This seems to be a common problem, but the solution is typically using getInfo function to bring these values over to client side. Unfortunately getInfo returns a null in this case.
The code below is for a collection of images OR a single image. The single image(image1) returns an image with an extra property(waterArea), and the mapped algorithm blows up(because the function is returning nulls).
I've also tried using getInfo on waterAg to potentially bring that list over to client side, however that returns the same List of objects that I don't want.
var image1 = ee.Image(leastcloud.first()).select(['B11','B8','B3'])
var stackarea = function(image){
var watermask = ee.Image(0)
var MNDWI = image.normalizedDifference(['B3','B11'])
watermask = watermask.where(MNDWI.gt(.31),1);
//sum of water pixels in an area
var sum = ee.Number(watermask.reduceRegion({
reducer: ee.Reducer.sum(),
geometry: geometry,
scale: 20,
maxPixels: 1e9
}));
var clientSide = sum.getInfo()
var setArea = image.set('waterArea', clientSide)
return setArea
};
var single = stackarea(image1)
print(single)
var watermapped = filterSpot.map(stackarea)
var waterAg = watermapped.aggregate_array('waterArea')
print(waterAg)
I'm really not sure how to extract these values as numbers...
I'm hoping to get a list of numbers so that I can concatenate that array to other arrays(date of image, cloud pixel %, etc.)
reduceRegion returns a dictionary object, not a number-like object. Therefore, in your stackarea function, clientSide variable is a dictionary (i.e. an object), not a number.
The number that you're after is stored in the dictionary returned by the reduceRegion function. You can get your hand on that number by using a get function on this dictionary object:
var sum = watermask.reduceRegion({
reducer: ee.Reducer.sum(),
geometry: geometry,
scale: 20,
maxPixels: 1e9
}).get('nd');
In this way, sum will be a server-side number that store the value you're after (There's no need to use ee.Number here as it does not help much).
In case you wonder about why using get('nd') but not get('somethingelse'), well it's the name of the band in your watermask image, and this name is the default band name given to the result of the normalizedDifference function.
And in my opinion, you don't even need to use the getInfo function which takes much more time to execute. Just delete the line var clientSide = sum.getInfo() and modify the next line into var setArea = image.set('waterArea', sum).
Hope this help.
Related
firstly apologies: I am a beginner in Earth Engine, but googling my question hasn't yielded any results. I have a reasonable amount of experience with other languages/platforms.
I have a table of data with headers 'name' and 'value' with N entries, I also have a multiband images in which the bands are named the same as the 'name' column in my table.
I want to apply a functions to each band in the image, based on its corresponding value in the table.
I'm struggling to find a way to do this without using loops and getInfo(), both of which I understand are not efficient and generally frowned upon.
I think perhaps I'm missing something fundamental here regarding the interaction between local variables and things occuring serverside - help would be greatly appreciated!
You could perhaps iterate over the band names in the image:
var updatedImage = ee.Image(
image.bandNames().iterate(
function (bandName, acc) {
bandName = ee.String(bandName) // Must cast from ee.Element to actual type
var feature = features
.filter(ee.Filter.eq('name', bandName))
.first()
var value = feature.getNumber('value')
var bandWithFunctionApplied = image.select(bandName)
.add(value) // Apply some function
return ee.Image(acc)
.addBands(bandWithFunctionApplied)
},
ee.Image([])
)
)
https://code.earthengine.google.com/082411908a7525a4c8a87916b5ea88fc
// I have a custom metadata object named boatNames__mdt and I'm using two methods to get a list of picklist values in a String[];
First Method
Map<String, boatNames__mdt> mapEd = boatNames__mdt.getAll();
string boatTypes = (string) mapEd.values()[0].BoatPick__c;
// BoatPick__c is a textarea field (Eg: 'Yacht, Sailboat')
string[] btWRAP = new string[]{};
**btWRAP**.addAll(boatTypes.normalizeSpace().split(','));
Second Method
string[] strL = new string[]{};
Schema.DescribeFieldResult dfr = Schema.SObjectType.boatNames__mdt.fields.BoatTypesPicklist__c;
// BoatTypesPicklist__c is a picklist field (Picklist Values: 'Yacht, Sailboat')
PicklistEntry[] picklistValues = dfr.getPicklistValues();
for (PicklistEntry pick : picklistValues){
**strl**.add((string) pick.getLabel());
}
Map with SOQL query
Map<Id, BoatType__c> boatMap = new Map<Id, BoatType__c>
([Select Id, Name from BoatType__c Where Name in :btWRAP]);
When I run the above Map with SOQL query(btWRAP[]) no records show up.
But when I used it using the strl[] records do show up.
I'm stunned!
Can you please explain why two identical String[] when used in exact SOQL queries behave so different?
You are comparing different things so you get different results. Multiple fails here.
mapEd.values()[0].BoatPick__c - this takes 1st element. At random. Are you sure you have only 1 element in there? You might be getting random results, good luck debugging.
normalizeSpace() and trim() - you trim the string but after splitting you don't trim the components. You don't have Sailboat, you have {space}Sailboat
String s = 'Yacht, Sailboat';
List<String> tokens = s.normalizeSpace().split(',');
System.debug(tokens.size()); // "2"
System.debug(tokens); // "(Yacht, Sailboat)", note the extra space
System.debug(tokens[1].charAt(0)); // "32", space's ASCII number
Try splitting by "comma, optionally followed by space/tab/newline/any other whitespace symbol": s.split(',\\s*'); or call normalize in a loop over the split's results?
pick.getLabel() - in code never compare using picklist labels unless you really know what you're doing. Somebody will translate the org to German, French etc and your code will break. Compare to getValue()
I want to get possible combinations of two sets of lists in google earth engine, but my code did not works.
var Per1= ee.Array([[0.1,0.5,0.8],[0.4,0.5,0.2]])
var pre = PercFin1.toList()
var CC=ee.List([1,2,3]);
var ZZ = pre.map(function(hh){
var Per11 = ee.List(pre).get(hh);
var out = CC.zip(Per11);
return out;
});
print (ZZ)
The error I get is:
List.get, argument 'index': Invalid type. Expected: Integer. Actual: List.
Thanks in advance
I don't know if this is what you want, but it looks like you've got the right idea but made an incidental mistake: hh is not an index into pre but an element of it.
I modified and simplified the last part of your code (along with changing PercFin1 to Per1, which I assume was a typo):
var ZZ = pre.map(function(hh){
return CC.zip(hh);
});
print(ZZ);
The result of this is
[
[[1,0.1],[2,0.5],[3,0.8]],
[[1,0.4],[2,0.5],[3,0.2]]
]
which is what I understand you want — each row in Per1 individually zipped with CC.
the following is my problem:
I do a select on my database and want to write the values of every record i get in a map. When i do this, i only have the values of one record in my map, because the put() function overwrites the entries everytime the loop starts again. Since I have to transfer the Key:Value pairs via JSON into my Javascript and write something into a field for every Key:Value pair, an ArrayList is not an option.
I've already tried to convert a ArrayList, which contains the Map, to a Map or to a String and then to Map, but i failed.
EDIT:
Here´s my Code
def valueArray = new ArrayList();
def recordValues = [:]
while (rs.next())
{
fremdlKorr = rs.getFloatValue(1)
leistungKorr = rs.getFloatValue(2)
materialKorr = rs.getFloatValue(3)
strid = rs.getStringValue(4)
recordValues.put("strid", strid);
recordValues.put("material", materialKorr);
recordValues.put("fremdl", fremdlKorr);
recordValues.put("leistung", leistungKorr);
valueArray.add(korrekturWerte);
}
The ArrayList was just a test, i dont want to have an ArrayList, i need a Map.
The code as written, will give you a list of maps, but the maps will all contain the values of the last row. The reaons is the def recordValues = [:] that is outside of the while loop. So you basically add always the same map to the list and the map values get overwritten each loop.
While moving the code, would fix the problem, I'd use Sql instead. That all boils down to:
def valueArray = sql.rows("select strid, material, fremdl, leistung from ...")
From a linter provider, I receive a Point compatible array(line, column) where the error occured. Now I would like to hightlight the word surrounding that point, basically the result one would get if that exact point was double-clicked in the editor. Something like
const range = textEditor.getWordAtPosition(point)
Is what I hoped for, but couldn't find in the documentation.
Thanks for your help!
After looking around for a while, there seems to be no API method for the given need. I ended up writing a small helper function based upon this answer:
function getWordAtPosition(line, pos) {
// Perform type conversions.
line = String(line);
pos = Number(pos) >>> 0;
// Search for the word's beginning and end.
const left = Math.max.apply(null, [/\((?=[^(]*$)/,/\)(?=[^)]*$)/, /\,(?=[^,]*$)/, /\[(?=[^[]*$)/, /\](?=[^]]*$)/, /\;(?=[^;]*$)/, /\.(?=[^.]*$)/, /\s(?=[^\s]*$)/].map(x => line.slice(0, pos).search(x))) + 1
let right = line.slice(pos).search(/\s|\(|\)|\,|\.|\[|\]|\;/)
// The last word in the string is a special case.
if (right < 0) {
right = line.length - 1
}
// Return the word, using the located bounds to extract it from the string.
return str.slice(left, right + pos)
}
Here, the beginning of the word is determined by the latest occurance of one of the characters (),.[]; or a blank.
The end of the word is determined by the same characters, however here the first occurance is taken as a delimeter.
Given the original context, the function can the be called using the API method ::lineTextForBufferRow and the desired postion (column) as follows:
const range = getWordAtPosition(textEditor.lineTextForBufferRow(bufferRow), 10)