QGIS/C4/Nearest-Neighbour-Analysis/English-timed

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Time Narration
00:01 Welcome to this tutorial on Nearest Neighbour Analysis in QGIS.
00:07 In this tutorial, we will learn about
00:11 Nearest Neighbour Analysis by Distance matrix method.
00:16 Statistics using Nearest Neighbour Analysis tool.
00:21 Here I am using,

Ubuntu Linux OS version. 16.04

QGIS version 2.18

00:32 To follow this tutorial learner must be familiar with QGIS interface.
00:39 For pre-requisite QGIS tutorials, please use this link.
00:45 The files required to practise this tutorial are available in the Code files link.
00:52 Please download and extract the contents of the folder.
00:57 Here I have the folder with the required file to practise this tutorial.
01:04 Double-click to open the folder.

Here you will find, Urban areas.shp and Volcanoes.shp.

01:15 Volcanoes.shp layer shows active volcanoes in the world.
01:21 Urban areas.shp shows populated urban areas of the world.
01:28 Open the two shape files in QGIS, select both the files.
01:35 Right-click and select Open with QGIS Desktop option from the context menu.
01:42 QGIS interface opens with two layers loaded in the layers panel.
01:49 Right-click on the volcanoes layer and select zoom to layer option.
01:55 On the canvas you will see a map with point features.
02:01 Let us label these point features.
02:05 Right-click on Volcanoes layer, from the sub menu click on Properties.
02:12 Layer Properties dialog-box opens.
02:16 Select Labels from the left panel.
02:20 Select Show labels for this layer option from the drop down.
02:25 In the Label with drop down select Name.
02:29 Here you will find various options to modify the label style.
02:34 Choose the required style and click on OK button.
02:39 On the canvas, points with the names is displayed.
02:44 Similarly let us label Urban areas.
02:51 On the canvas point features are labeled with their cities.
02:57 QGIS has tools to analyze spatial relationships between features.
03:04 One such tool is Nearest Neighbour Analysis.
03:08 Nearest Neighbour Analysis is used for the following analysis.
03:13 Finding distance between two Point features.
03:17 Finding features which are closest to a given feature.
03:23 First, we will create distance matrix for calculating the distances.
03:29 Let us open the attribute table for the Volcanoes layer.
03:34 Right-click on Volcanoes layer.
03:37 Select Open Attribute Table.
03:40 In the attribute table there are multiple columns.
03:45 Various attributes for the point features are listed here.
03:50 Names of the volcanoes and their locations are also listed here.
03:56 Close the attribute table.
03:59 Open the attribute table for the Urban areas layer.
04:04 Notice the various columns in the table.
04:08 You will find names of the cities, countries and other information in this table.
04:15 Close the attribute table.
04:18 Let us calculate the distance between the active volcanoes and nearest cities.
04:24 Click on Vector menu.
04:27 Select Analysis Tools.
04:30 Select Distance Matrix option from the sub-menu.
04:34 Distance Matrix dialog-box opens.
04:38 Please read the description about Distance matrix on the right-panel.
04:44 By default Parameters tab opens on the screen.
04:49 Select the Parameters as shown here.
04:53 Select Volcanoes as an Input Point Layer.
04:58 Select NAME as Input unique ID field
05:03 Select Urban Areas as Target Point Layer.
05:08 Select City as Target unique ID field.
05:13 Keep Output matrix type as Linear.
05:17 Let us find the distance from the volcano to two nearest cities.
05:23 Hence, select 2 in Use only the nearest target Points field.
05:30 Click on the 3 dots button next to Distance Matrix field.
05:35 From the drop-down menu, select Save to file. option.
05:40 In the dialog-box, give an appropriate name and location.
05:44 Choose Files of type, as CSV .
05:49 In the Encoding field choose System.

Click on Save button.

05:56 In the Distance matrix dialog-box check the check-box for the following.

Open output file after running algorithm.

06:06 Click on the Run button at the bottom-right corner of the dialog box.
06:12 The process will take few seconds.
06:15 A new csv layer named as Distance matrix is added in the Layers panel.
06:22 Open the attribute table for Distance matrix layer.
06:27 In the attribute table there are three columns.

The last column is the distance between the volcano and nearest city.

06:38 Please note, here the distance is in meters.
06:43 This is because the layers are projected in WGS 84 UTM Zone 46N system.
06:52 Depending on the CRS, the distance can also be in layer units or in degrees.
07:00 Also observe that for each volcano, two nearest cities are listed.
07:07 Let us get some statistical analysis for the layers using Nearest neighbour tool.
07:14 We will run a nearest neighbour analysis to analyze the distribution of features.
07:21 The results will establish, the distribution as clustered, dispersed or random.
07:29 Close the attribute table.
07:32 Click on Vector menu.
07:35 Scroll down and click on the Analysis Tools.
07:40 From the sub-menu, select the Nearest Neighbour analysis.
07:46 Nearest Neighbour Analysis dialog-box opens.
07:50 Read the information given about Nearest neighbour analysis on the right-panel.
07:57 Select Volcanoes layer in the Points drop-down.
08:02 Click on Run button at the bottom-right corner.
08:06 Results window opens.
08:09 Some statistical parameters for the volcanoes layer are listed here.
08:15 Observed mean distance
08:17 Expected mean distance
08:20 Nearest neighbour index
08:23 Number of point features and

Z-Score.

08:29 The Nearest Neighbour Index is expressed as the ratio of the Observed Mean Distance to the Expected Mean Distance.
08:39 If the index value is less than 1, the pattern exhibits clustering.
08:45 If the index value is greater than 1, the trend is towards dispersion.
08:52 Here the Nearest Neighbor Index value of 0.2 indicates clustering.

Which means, the volcanoes are located close to each other.

09:04 Similarly a negative Z-Score also indicates clustering of point features.
09:10 Close the Results window.
09:13 Save the project using Project menu.
09:17 Let us summarize.
09:19 In this tutorial we have learnt about,
09:22 Nearest Neighbour Analysis by Distance Matrix method.

Statistics using Nearest Neighbour Analysis tool.

09:32 As an assignment, Create Distance Matrix for nearest 5 volcanoes to urban areas.

Hint: Use Urban Areas as Input and K as 5.

09:46 Your completed assignment should look as shown here.
09:51 The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

09:59 The Spoken Tutorial project team conducts workshops and gives certificates. For more details please write to us.
10:09 Please post your timed queries in this forum.
10:13 The Spoken Tutorial Project is funded by, MHRD Government of India.
10:20 This tutorial is contributed by Ambadas Maske from College of Engineering Pune, Snehalatha Kaliappan and Himanshi Karwanje from IIT Bombay.

Thank you for joining.

Contributors and Content Editors

PoojaMoolya