### Land Cover Mapping - Part 4 (Analyze Statistics)

###### Published on Jun 08, 2020 | Bikesh Bade | 1341 Views

Statistics are simple tools that helps us for a better understanding of our images. Spatial statistics is one of the most rapidly growing areas of statistics.

#### How to get Statistics of the Classified Image?

To get statistics of  classified image and its pixel values in a region, google earth engine use `image.reduceRegion()`. This reduces all the pixels in the region(s) to a statistic or other compact representation of the pixel data in the region (e.g. histogram). The region is represented as a `Geometry`, which might be a polygon, containing many pixels, or it might be a single point, in which case there will only be one pixel in the region.

#### Pixels in the region

Pixels are determined to be in the region (and weighted) according to the following rules, applied in the specified scale and projection:

• Unweighted reducers
•  ee.Reducer.count() or
• ee.Reducer.mean().unweighted()
• pixels are included if their centroid is in the region and the image's mask is non-zero.

• Weighted reducers
• (e.g. ee.Reducer.mean())
• pixels are included if at least (approximately) 0.5% of the pixel is in the region and the image's mask is non-zero
• their weight is the minimum of the image's mask and the (approximate) fraction of the pixel covered by the region.

```//classified is the image that is classified using any Machine learning
var stats = classified.reduceRegion({
reducer: ee.Reducer.count(), //Gives you the count it has other variable like sum()
geometry: studyArea,
scale: 30
});
print(stats);
```

Get Number of pixels in each class of classified image with the histogram

```var options = {
lineWidth: 1,
pointSize: 2,
hAxis: {title: 'Classes'},
vAxis: {title: 'Num of pixels'},
title: 'Number of pixels in each class.', // title
colors:['#ecf0f1','#27ae60', '#f1c40f','#16a085','#e74c3c','#2980b9'], //color pallete

};

//create a histogram with pixel count of each class
var pixelChart = ui.Chart.image.byClass({
classBand: 'classification',
region: studyArea,
scale: 90,
reducer: ee.Reducer.count() //Gives you the count it has other variable like sum()
}).setSeriesNames(['Snow', 'Forest', 'Cropland','Grassland', 'Residential', 'Water Bodies' ])
.setOptions(options);

print(pixelChart)
```

Get area of each class just by multiplying with 30 *30 in case of lansat

Get a link to the code

Code for Import data

Code for Topology

Code for getting Indexes

#### John Ogbodo

Many thanks for your mentoring. I would like to learn on you to become an Google engine expert. What will that cost me? John

• Jun 08, 2020 |