# GEE code to compute mean annual NDVI time series

Geographic Information Systems## How do you calculate NDVI from Gee?

As mentioned in the previous chapter, the NDVI is the normalized difference of the red and the infrared band, calculated as **NDVI = (NIR-RED) / (NIR+RED)**.

## How do you make a time series graph on Google Earth Engine?

**Use ui.** **Chart.** **image.** **series** to display an image time series for a given region; each image band is presented as a unique series.

## How to learn Google Earth Engine?

If you have not already, you will need to enable access by logging in using a registered Google account. **Navigate to the Scripts tab located on the far left of the Code Editor**. There you will find a collection of example scripts that access, display, and analyze Earth Engine data.

## How to calculate NDVI in Python?

**Calculate NDVI in Python**

- import os import matplotlib.pyplot as plt import numpy as np import rioxarray as rxr import geopandas as gpd import earthpy as et import earthpy.spatial as es import earthpy.plot as ep # Download data and set working directory data = et.
- naip_data_path = os.
- naip_ndvi = es.
- ep.
- ep.

## How do I extract NDVI values?

In this tutorial, we will extract NDVI values from a raster time series dataset in R and plot them using ggplot .**Install R Packages**

- raster: install.packages(“raster”)
- rgdal: install.packages(“rgdal”)
- ggplot2: install.packages(“ggplot2”)
- More on Packages in R – Adapted from Software Carpentry.

## What graph is best for time series?

line graph

**A line graph** is the simplest way to represent time series data. It helps the viewer get a quick sense of how something has changed over time.

## How do you plot a time series analysis?

**5 types of plots that will help you with time series analysis**

- are there any patterns in the data?
- are there any unusual observations (outliers)?
- do the properties of the series of observations change over time (non-stationarity)?
- are there any relationships between the variables?

## How do you graph a time series?

**In order to draw a time series graph:**

- Draw and label a horizontal scale based on the time intervals of the data provided.
- Draw and label the vertical axis, choosing an appropriate scale.
- Plot the points and join with straight line segments.

## How is NDVI derived?

NDVI is **calculated from the visible and near-infrared light reflected by vegetation**. Healthy vegetation (left) absorbs most of the visible light that hits it, and reflects a large portion of the near-infrared light. Unhealthy or sparse vegetation (right) reflects more visible light and less near-infrared light.

## What is the common range of NDVI values for green vegetation?

Although there are several vegetation indices, one of the most widely used is the Normalized Difference Vegetation Index (NDVI). NDVI values range from **+1.0 to -1.0**.

## How do you calculate the area of a gee?

We can calculate the area of the image by **counting the total number of unmasked pixels in that image.** **Then, multiply the total number of unmasked pixels by the scale factor to get the area in square meters**.

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