Google Earth Engine ui.Chart.getDataTable() returns empty list

Question

I am trying to grab the underlying data from a chart in GEE. It looks like there is a built in method for this: ui.Chart.getDataTable(), however it appears to not work. I've tried on multiple charts. Here's the documentation for the function. Here is my code:

var start = '2021-01-01';
var end = '2022-12-31';

// Construct a polygon from a list of x,y coordinate pairs defining a boundary.
var roi2 = ee.Geometry.Polygon(
  [-110.0, 40, -113.0, 40, -110.0, 42]
);
Map.addLayer(roi2, {}, 'roi2');
Map.centerObject(roi2)

// Snow water equivalent - daily
var dayMet = ee.ImageCollection("NASA/ORNL/DAYMET_V4")
  .filterBounds(roi2)
  .select('prcp', 'swe')   
  .filterDate(start, end)

// Save the chart as a variable
var dayMetChart = (ui.Chart.image.series(dayMet.select(['prcp', 'swe']), roi,
      ee.Reducer.mean(), 4000)
  .setOptions({
    title: 'dayMet',
    lineWidth: 1,
    pointSize: 3
  })
);

// Use the getDataTable function and print the data
var table = dayMetChart.getDataTable();
print(table)

The table variable is an empty object. Can someone explain why this doesn't work or how to get it to work?

Answer 1

It looks as a bug not fixed yet. However, you can use 'reduceRegion', as follows, for obtaining each column used to print the chart.

var dayMet_lst = dayMet.toList(dayMet.size());

var datatable = dayMet_lst.map(function (ele){
  
  var date = ee.Date(ee.Image(ele).get("system:time_start")).format().slice(0,10);
  
  var values = ee.Image(ele).reduceRegion(ee.Reducer.mean(), roi2, 4000);
  
  return [date, values.get('prcp'), values.get('swe')];
  
});

print('datatable', datatable);

After running complete code, it can be obtained the following result. Data table was printed as a list with three columns: date, prcp and swe.