PoojaMoolya: Created page with "{|border=1 |- ||'''Time''' || '''Narration''' |- ||00:01 ||Welcome to this tutorial on '''Nearest Neighbour Analysis''' in ''' QGIS'''. |- ||00:07 ||In this tutorial, we will..."

2020-12-21T05:26:23Z

Created page with "{|border=1 |- ||'''Time''' || '''Narration''' |- ||00:01 ||Welcome to this tutorial on '''Nearest Neighbour Analysis''' in ''' QGIS'''. |- ||00:07 ||In this tutorial, we will..."

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{|border=1
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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

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|| 00:11
|| '''Nearest Neighbour Analysis '''by '''Distance matrix''' method.

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|| 00:16
||'''Statistics''' using '''Nearest Neighbour Analysis''' tool.

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|| 00:21
||Here I am using,

'''Ubuntu Linux '''OS version. 16.04

'''QGIS '''version''' 2.18
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|| 00:32
||To follow this tutorial learner must be familiar with '''QGIS '''interface.

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|| 00:39
||For pre-requisite QGIS tutorials, please use this link.

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|| 00:45
||The files required to practise this tutorial are available in the '''Code files''' link.

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|| 00:52
||Please download and extract the contents of the folder.

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||00:57
||Here I have the folder with the required file to practise this tutorial.

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|| 01:04
||Double-click to open the folder.

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

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|| 01:15
||'''Volcanoes.shp''' layer shows active volcanoes in the world.

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|| 01:21
||'''Urban areas.shp''' shows populated urban areas of the world.

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|| 01:28
||Open the two shape files in QGIS, select both the files.

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|| 01:35
||Right-click and select '''Open with QGIS Desktop''' option from the context menu.

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|| 01:42
||QGIS interface opens with two layers loaded in the layers panel.

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|| 01:49
||Right-click on the '''volcanoes '''layer and select '''zoom to layer''' option.

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||01:55
||On the canvas you will see a map with point features.

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|| 02:01
|| Let us label these point features.

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|| 02:05
|| Right-click on '''Volcanoes layer''', from the sub menu click on '''Properties'''.

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|| 02:12
|| '''Layer Properties''' dialog-box opens.

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|| 02:16
|| Select '''Labels''' from the left panel.

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|| 02:20
|| Select '''Show labels for this layer''' option from the drop down.

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|| 02:25
|| In the '''Label with '''drop down select '''Name'''.

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|| 02:29
||Here you will find various options to modify the label style.

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|| 02:34
||Choose the required style and click on '''OK '''button.
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|| 02:39
|| On the canvas, points with the names is displayed.

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|| 02:44
|| Similarly let us label '''Urban areas'''.

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|| 02:51
|| On the canvas point features are labeled with their cities.

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|| 02:57
||QGIS has tools to analyze spatial relationships between features.

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|| 03:04
||One such tool is '''Nearest Neighbour Analysis. '''

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|| 03:08
||'''Nearest Neighbour Analysis '''is used for the following analysis.

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|| 03:13
||Finding distance between two '''Point features'''.

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|| 03:17
|| Finding features which are closest to a given feature.

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|| 03:23
||First, we will create '''distance matrix''' for calculating the distances.

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|| 03:29
||Let us open the''' attribute''' table for the '''Volcanoes''' layer.

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|| 03:34
||Right-click on '''Volcanoes''' layer.

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|| 03:37
||Select '''Open Attribute Table'''.

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|| 03:40
||In the '''attribute table''' there are multiple columns.

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|| 03:45
||Various attributes for the point features are listed here.

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|| 03:50
||Names of the volcanoes and their locations are also listed here.

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|| 03:56
||Close the '''attribute table'''.

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|| 03:59
||Open the '''attribute table''' for the '''Urban areas''' layer.

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|| 04:04
||Notice the various columns in the table.

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|| 04:08
||You will find names of the cities, countries and other information in this table.

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|| 04:15
||Close the '''attribute table'''.
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|| 04:18
||Let us calculate the distance between the active volcanoes and nearest cities.

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|| 04:24
||Click on '''Vector''' menu.

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|| 04:27
||Select '''Analysis Tools'''.

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|| 04:30
||Select '''Distance Matrix''' option from the sub-menu.

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|| 04:34
||'''Distance Matrix''' dialog-box opens.

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|| 04:38
||Please read the description about '''Distance matrix''' on the right-panel.

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|| 04:44
||By default '''Parameters '''tab opens on the screen.

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|| 04:49
||Select the Parameters as shown here.

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|| 04:53
||Select '''Volcanoes''' as an '''Input Point Layer'''.

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|| 04:58
||Select '''NAME''' as '''Input unique ID field '''

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|| 05:03
||Select '''Urban Areas '''as''' Target Point Layer'''.

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|| 05:08
||Select '''City''' as '''Target unique ID field'''.

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|| 05:13
||Keep''' Output matrix type''' as '''Linear'''.

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|| 05:17
||Let us find the distance from the volcano to two nearest cities.

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|| 05:23
||Hence, select 2 in '''Use only the nearest target Points''' field.

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|| 05:30
||Click on the 3 dots button next to '''Distance Matrix''' field.

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|| 05:35
||From the drop-down menu, select '''Save to file'''. option.

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|| 05:40
||In the dialog-box, give an appropriate name and location.

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|| 05:44
||Choose''' Files of type''', as''' CSV '''.

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|| 05:49
||In the '''Encoding''' field choose '''System'''.

Click on '''Save''' button.

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

'''Open output file after running algorithm'''.

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|| 06:06
||Click on the '''Run '''button at the bottom-right corner of the dialog box.

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|| 06:12
||The process will take few seconds.

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|| 06:15
||A new '''csv layer''' named as '''Distance matrix''' is added in the '''Layers''' panel.

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|| 06:22
||Open the '''attribute table''' for '''Distance matrix''' layer.

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|| 06:27
||In the '''attribute table''' there are three columns.

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

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|| 06:38
||Please note, here the distance is in meters.

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|| 06:43
||This is because the layers are projected in '''WGS 84 UTM Zone 46N system'''.

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|| 06:52
||Depending on the '''CRS''', the distance can also be in '''layer units''' or in '''degrees'''.

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|| 07:00
||Also observe that for each volcano, two nearest cities are listed.

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||07:07
||Let us get some statistical analysis for the layers using '''Nearest neighbour tool'''.

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|| 07:14
||We will run a '''nearest neighbour analysis''' to analyze the distribution of features.

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|| 07:21
||The results will establish, the distribution as clustered, dispersed or random.
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|| 07:29
||Close the '''attribute table'''.

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|| 07:32
||Click on '''Vector''' menu.

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|| 07:35
||Scroll down and click on the '''Analysis Tools'''.

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|| 07:40
||From the sub-menu, select the '''Nearest Neighbour analysis'''.

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|| 07:46
||'''Nearest Neighbour Analysis''' dialog-box opens.

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|| 07:50
||Read the information given about '''Nearest neighbour analysis''' on the right-panel.

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|| 07:57
||Select '''Volcanoes''' layer in the '''Points''' drop-down.

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|| 08:02
||Click on '''Run''' button at the bottom-right corner.

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|| 08:06
||'''Results''' window opens.

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|| 08:09
||Some statistical parameters for the volcanoes layer are listed here.

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||08:15
||'''Observed mean distance'''

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|| 08:17
||'''Expected mean distance'''

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|| 08:20
||'''Nearest neighbour index'''

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|| 08:23
||'''Number of point features''' and

'''Z-Score'''.
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|| 08:29
||The '''Nearest Neighbour Index''' is expressed as the ratio of the '''Observed Mean Distance''' to the '''Expected Mean Distance'''.

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|| 08:39
||If the index value is less than 1, the pattern exhibits clustering.

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|| 08:45
||If the index value is greater than 1, the trend is towards dispersion.

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|| 08:52
||Here the '''Nearest Neighbor Index''' value of 0.2 indicates clustering.

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

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|| 09:04
||Similarly a negative '''Z-Score''' also indicates clustering of point features.

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|| 09:10
||Close the '''Results''' window.

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|| 09:13
||Save the project using '''Project''' menu.

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|| 09:17
||Let us summarize.

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|| 09:19
||In this tutorial we have learnt about,

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|| 09:22
||'''Nearest Neighbour Analysis''' by '''Distance Matrix''' method.

Statistics using '''Nearest Neighbour Analysis''' tool.

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|| 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.

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|| 09:46
||Your completed assignment should look as shown here.

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|| 09:51
||The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

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|| 09:59
||The Spoken Tutorial project team conducts workshops and gives certificates. For more details please write to us.

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|| 10:09
||Please post your timed queries in this forum.

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|| 10:13
||The Spoken Tutorial Project is funded by''', MHRD''' '''Government''' of India.

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|| 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.
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|}

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

PoojaMoolya: Created page with "{|border=1 |- ||'''Time''' || '''Narration''' |- ||00:01 ||Welcome to this tutorial on '''Nearest Neighbour Analysis''' in ''' QGIS'''. |- ||00:07 ||In this tutorial, we will..."