the function .map applies a function to every individual image in an ImageCollection. And the function .iterate applies a function to one image and the output of the calculation done to the precedent image on an ImageCollection.
The first only works with one image each time, and the second implies modifying each image and utilize it to any calculation with the next one.
I need a function that works like .iterate, but does not modify the precedent image. I just need to do:
image (time -1) / image (time 0).
I can not find a way to do it,
thanks for your help
i have tried,
var first = ee.List([
ee.Image(1).set('system:time_start', time0).select([0], ['pc1'])
]);
var changeDET = function(image, list) {
var previous = ee.Image(ee.List(list).get(-1));
var change = previous.divide(image.select('pc1'))
.set('system:time_start', image.get('system:time_start'));
return ee.List(list).add(change);
};
var cumulative = ee.ImageCollection(ee.List(imageCollection.iterate(changeDET, first)))
.sort('system:time_start', false)
What you can do is to convert your imageCollection into a ee.List object, then map over that list with an index variable to access the previous image. Example code is below:
var length = yourImageCollection.size();
var list = yourImageCollection.toList(length);
var calculated_list = list.map(function(img) {
var index = list.indexOf(img)
img = ee.Image(img);
var previousIndex = ee.Algorithms.If(index.eq(0), index, index.subtract(1));
var previousImage = ee.Image(list.get(previousIndex)):
var change = ee.Image(previousImage.divide(img)
.copyProperties(img, ["system:time_start"]));
return change;
})
I'm not sure what you want to do with the first image, so when map function reach the first image, previousIndex will equal to index. In other words, the first image will be divided by itself (as there is no image before it).
Hope this helps.
Related
As a newbie to the google earth engine, I have been trying something (https://code.earthengine.google.com/6f45059a59b75757c88ce2d3869fc9fd) following a NASA tutorial (https://www.youtube.com/watch?v=JFvxudueT_k&ab_channel=NASAVideo). My last line (line 60) shows image.filter is not a function, while the one in the tutorial (line 34) is working. I am not sure what happened and how to sort this out?
//creating a new variable 'image' from the L8 collection data imported
var image = ee.Image (L8_tier1 //the details in the data will represent that the band resolution is 30m
//the details in the data will represent that the band resolution is 30m
//.filterDate ("2019-07-01","2021-10-03") //for a specific date range. maybe good to remove it for the function.
//the details in the data will represent that the band resolution is 30m
//the details in the data will represent that the band resolution is 30m
//.filterDate ("2019-07-01","2021-10-03") //for a specific date range. maybe good to remove it for the function.
.filterBounds (ROI) //for the region of interest we are interested in
//.sort ("COLUD_COVER") //for sorting the data between the range with a cloud cover, the metadata property we are interested in. Other way to do this is using the function below.
//.first() //this will make the image choose the first image with the least amount of cloud cover for the area. Other way to do this is using the function below.
);
//print ("Hague and Rotterdam", image); //printing the image in the console
//console on the right hand side will explain everything from the data
//id will show the image deatils and date of the image, for this case 29th July 2019
//under the properties tab cloud cover can be found, this is the least we can get for this area during this period
// //vizualisation of the data in the map with true color rendering
// var trueColour = {
// bands:["SR_B4","SR_B3","SR_B2"],
// min: 5000,
// max: 12000
// };
// Map.centerObject (ROI, 12); //for the centering the area in the center of the map with required zoom level
// Map.addLayer (image, trueColour, "Hague and Rotterdam"); //for adding the image with the variable of bands we made and naming the image
//Alternate way
//Function to cloud mask from the qa_pixel band of Landsat 8 SR data. In this case bits 3 and 4 are clouds and cloud shadow respectively. This can be different for different image sets.
function maskL8sr(image) {
var cloudsBitMask = 1 << 3; //remember to check this with the source
var cloudshadowBitMask = 1 << 4; //remember to check this with the source
var qa = image.select ('qa_pixel'); //creating the new variable from the band of the source image
var mask = qa.bitwiseAnd(cloudsBitMask).eq(0) //making the cloud equal to zero to mask them out
.and(qa.bitwiseAnd(cloudshadowBitMask).eq(0)); //making the cloud shadow equal to zero to mask them out
return image.updateMask(mask).divide(10000)
.select("SR_B[0-9]*")
.copyProperties(image, ["system:time_start"]);
}
// print ("Hague and Rotterdam", image);// look into the console now. How many images the code have downloaded!!!
//filtering imagery for 2015 to 2021 summer date ranges
//creating joint filter and applying to image collection
var sum21 = ee.Filter.date ('2021-06-01','2021-09-30');
var sum20 = ee.Filter.date ('2020-06-01','2020-09-30');
var sum19 = ee.Filter.date ('2019-06-01','2019-09-30');
var sum18 = ee.Filter.date ('2018-06-01','2018-09-30');
var sum17 = ee.Filter.date ('2017-06-01','2017-09-30');
var sum16 = ee.Filter.date ('2016-06-01','2016-09-30');
var sum15 = ee.Filter.date ('2015-06-01','2015-09-30');
var SumFilter = ee.Filter.or(sum21, sum20, sum19, sum18, sum17, sum16, sum15);
var allsum = image.filter(SumFilter);
Filtering is an operation you can do on ImageCollections, not individual Images, because all filtering does is choose a subset of the images. Then, in your script, you have (with the comments removed):
var image = ee.Image (L8_tier1
.filterBounds (ROI)
);
The result of l8_tier1.filterBounds(ROI) is indeed an ImageCollection. But in this case, you have told the Earth Engine client that it should be treated as an Image, and it believed you. So, then, the last line
var allsum = image.filter(SumFilter);
fails with the error you saw because there is no filter() on ee.Image.
The script will successfully run if you change ee.Image(...) to ee.ImageCollection(...), or even better, remove the cast because it's not necessary — that is,
var image = L8_tier1.filterBounds(ROI);
You should probably also change the name of var image too, since it is confusing to call an ImageCollection by the name image. Naming things accurately helps avoid mistakes, while you are working on the code and also when others try to read it or build on it.
Is there any way of knowing what constraints is a body attached to? I want to create a constraint each time two bodies collide, but not each time they collide after that first constraint is already created
UPDATE: Added proof of concept
In my code, i create an array of pairs with duplicate values, and because i have a maximum of 1000 elements, each value is duplicated in x+y1000 and y+x1000 indexes so they won't overlay
// global array
var alreadyPaired = [];
// on collision check, i save which pair of values must be paired
Matter.Events.on(engine, 'collisionStart', function(event) {
var idA = event.pairs[i].bodyA.id;
var idB = event.pairs[i].bodyB.id;
if ( !alreadyPaired[idA*1000+idB] && !alreadyPaired[idB*1000+idA] ) {
alreadyPaired[idA*1000+idB] = true;
alreadyPaired[idB*1000+idA] = true;
}
});
I want to plot the count of burn pixels for modis burned area product within my geometry regions called "table" for only agricultural pixels (obtained from 'lc' image collection). I couldn't find anything in the docs to indicate you can do such a query between 2 image collections. Anyone have any suggestions?
I have tried using a mask, but it seems that this might only work on individual ee.Image not between different image collections. The code is shown below:
var modba = ee.ImageCollection('MODIS/006/MCD64A1').filterDate('2017-01-
01', '2017-12-31').select('BurnDate')
var modbaN = ee.ImageCollection('MODIS/006/MCD64A1').filterDate('2017-01-
01', '2017-12-31').select('Uncertainty')
var lc = ee.ImageCollection('MODIS/006/MCD12Q1').filterDate('2017-01-01',
'2017-12-31').select('LC_Type1')
var AgOnly = lc.map(function(img) {
var ag = img.select('LC_Type1');
return ag.eq(12);
//Would also like to maybe have 2 or 3 LC types to select here
});
var mask_ba = modba.map(function(img){
return img.updateMask(AgOnly);
});
var bats =
//ui.Chart.image.seriesByRegion(modba, table, ee.Reducer.count());
ui.Chart.image.seriesByRegion(mask_ba, table, ee.Reducer.count());
print(bats);
var unts =
ui.Chart.image.seriesByRegion(modbaN, table, ee.Reducer.mean());
print(unts);
It's still doable with a wider date range and several land cover types.
In that case, just keep your old code that calculates AgOnly, and modify the code that calculates mask_ba as below:
var mask_ba = modba.map(function(img){
var img_year = img.date().format('YYYY');
var start_date = ee.Date(img_year.cat('-01-01'));
var end_date = start_day.advance(1, 'year');
var Agri_this_year = AgOnly.filterDate(start_date, end_date).max();
return img.updateMask(Agri_this_year);
});
Basically, the above code just extracts the year of the current img, then use filterDate method to select the land type cover of that year from AgOnly image collection, and finally apply updateMask.
The same idea could be applied to other land cover types.
Hope this helps.
As I understand, what you're trying to do is to mask each image in modba image collection (which has 12 images or one per month) by the corresponding image in AgOnly image collection (which has only 1 image for the whole year). That's totally doable.
In your provided code, you're updateMask using AgOnly (an image collection) which is not allowed by GEE.
All you need to do is just make AgOnly an image before using it for updateMask.
Try this:
var AgOnly = lc.map(function(img) {
var ag = img.select('LC_Type1');
return ag.eq(12);
//Would also like to maybe have 2 or 3 LC types to select here
}).max();
The max() method will convert your image collection into an image. You can also use min() or mean() if you like, which will all give the same result as there's only one image in AgOnl anyway.
Is it possible to do a DLT in CSS? If so, how is this accomplished? I can't think of a way using just transform: matrix... If this is not possible, what would be an alternative approach?
The particular effect I'm trying to achieve is laying out divs in a way similar to how Safari does this:
Here is a very rough and non-generic answer to your request. http://jsfiddle.net/3t5SM/
You could easily extend it to get a generic much better solution.
in my CSS,
#id1, #id4, #id7{
-webkit-transform: rotateY(40deg);
}
#id3, #id6, #id9{
-webkit-transform: rotateY(-40deg);
}
#id2, #id5, #id8{
-webkit-transform: scale(0.94);
}
the basic idea is to create a style for each column (here i'm calling the id's but again, it would be better to have a style for each column and define the columns as .left, .middle, .right, etc)
I'll update my post tonight if I have the time to go into the details :)
EDIT: as promise, here is a little better version. Now it is much more generic and depending on the size of your window, you'll get the right number of cubes. It is still far from being perfect (you could play with the size of the cubes in order to get a better depth feeling), but in general you see that it is possible, even dynamically :)
here is the fiddle: http://jsfiddle.net/P84qd/4/
To go a little into the details of the javascript:
function dispatch(){
var sizeOfImg = 150;
var windowWith = document.body.offsetWidth;
var widthRest = windowWith%sizeOfImg;
var nbSquareRow = Math.floor(windowWith/sizeOfImg);
dlt(nbSquareRow);
var marginVal = widthRest/(nbSquareRow+1);
var lineout = document.getElementById('lineout');
lineout.style.paddingLeft = marginVal+'px';
lineout.style.paddingTop = marginVal+'px';
var square = document.getElementsByTagName('div');
for(var i=0, length = square.length;i<length; i++){
if(square[i].className === 'square'){
square[i].style.marginRight = marginVal+'px';
square[i].style.marginBottom = marginVal+'px';
}
}
}
dispatch();
window.onresize = function(e){dispatch();};
function dlt(nbSquareRow){
var maxRotatDeg = 40;
var isEven=true;
if(nbSquareRow%2 == 0){
var unityRotatDeg = maxRotatDeg/(nbSquareRow/2);
}else{
var unityRotatDeg = maxRotatDeg/((nbSquareRow-1)/2);
isEven = false;
}
var middle = Math.floor(nbSquareRow/2);
var mySquares = document.getElementsByTagName('div');
for(var j=0, sqleng = mySquares.length;j<sqleng; j++){
if(mySquares[j].className == 'square'){
var colNumb = (parseInt(mySquares[j].id)-1)%nbSquareRow;
var myMultiplier = (middle-colNumb);
if(isEven && myMultiplier<=0){
myMultiplier--;
}
mySquares[j].style.webkitTransform = 'rotateY('+(unityRotatDeg*myMultiplier)+'deg)';
}
}
}
The dispatch function is a simple function that will distribute the squares on your web page with equal margins (top, left, right, bottom). I took it from 1.
The dlt function calculates the number of columns and defines the rotation amount for each column (in my example the maximum rotation value is 40). The rest of the code are purely some math checks in order to make it work correctly.
In order to get a better result, you should play with the size of each square, but be careful because the dispatch function also needs to know the size of the square to calculate how many squares will be allowed to be displayed per row. I'll let you have fun with it ;)
Here's the code I am using to blur an image using BitmapData. The function is called on a Slider_changeHandler(event:Event):voidevent and the value of the slider is passed to the function as blurvalue.
The problem is the function works but seems to be cummalative (if that's the correct word!), that is, suppose I slide it to the maximum and after that try to reduce the blur by sliding it back towards the front the blur still keeps increasing. How do I make it to work so when I will slide it up blur increases and when I slide it back blur decreases and when slider is at 0, no blur is applied.
var blur:BlurFilter = new BlurFilter();
blur.blurX = blurvalue;
blur.blurY = blurvalue;
blur.quality = BitmapFilterQuality.MEDIUM;
bitmapdata.applyFilter(bitmapdata,new
Rectangle(0,0,bitmapdata.width,bitmapdata.height),new Point(0,0),
blur);
return bitmapdata;
how about returning a clone of the original bitmapData with the filter applied ?
e.g.
var result:BitmapData = bitmapdata.clone();
var blur:BlurFilter = new BlurFilter();
blur.blurX = blurvalue;
blur.blurY = blurvalue;
blur.quality = BitmapFilterQuality.MEDIUM;
result.applyFilter(result,new
Rectangle(0,0,bitmapdata.width,bitmapdata.height),new Point(0,0),blur);
return result;
Also, if you're using the BlurFilter, you might need a larger rectangle, depending on the amount of blur. For that, you can use the generateFilterRect() method to get correct sized rectangle for the filter.
If I were you, I'd take the BitmapData and put it in a Bitmap object, then add the filters:
var bitmap:Bitmap = new Bitmap(bitmapData);
var blur:BlurFilter = new BlurFilter();
blur.blurX = blurvalue;
blur.blurY = blurvalue;
blur.quality = BitmapFilterQuality.MEDIUM;
bitmap.filters = [blur];
By doing this (interchanging the filters array), you're not making the filters cumulative.