# Different number of observations when using SampleRegions

I have a code in GEE which creates two images from sentinel-1 (SAR) and from sentinel-2 (NDVI) , creates from them paired image and then creates scatter plot from the two bands in the image. In order to create the scatterplot, I know I need to run kind of training and i'm a bit confused about it and about my results.

This is the code I have that seemed to be working:

``````
// make an image for the two variables
var pairedImage =  ee.ImageCollection.fromImages([imageNDVIcor,SARreproject]).toBands().rename(["NDVI","SAR"]);
print("pairedImage",pairedImage);
// Generate a sample of points within the region
var sample = pairedImage.sampleRegions(geometry, null, 150);
print("sample",sample);
// Generate chart from sample
var chart = ui.Chart.feature.byFeature(sample, 'NDVI', 'SAR')
.setChartType('ScatterChart');
print("chart",chart);

``````

The point is that I get results that look nice but I can't understand, for example: this is suppose to be my point? what is this? what are those values?

var sample = pairedImage.sampleRegions(geometry, null, 500); and this is with: var sample = pairedImage.sampleRegions(geometry, null, 150);: and this is when it's 1000: How come using less points lead to more ponts in the correlation? I feel confused and i'm afraid that I don't understand something very basic with the sample points.

My end goal is to understand why I have gotten those two different charts when 500 has lesspoints than 100 and 1000 had the least. what'shapenning here?

Here's the `sampleRegions()` function:
``````sampleRegions(collection, properties, scale, projection, tileScale, geometries)