Vector aggregate values - Revision history

Neteler at 20:55, 2 August 2013

2013-08-02T20:55:22Z

← Older revision		Revision as of 20:55, 2 August 2013
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	[[Category:FAQ]]		[[Category:FAQ]]
	[[Category:Vector]]		[[Category:Vector]]
	[[Category:~~Aggregation~~]]		[[Category:Statistics]]

⚠️NikosA: /* Method 2 */ use d.redraw after r.colors

2013-01-13T22:01:49Z

Method 2: use d.redraw after r.colors

← Older revision		Revision as of 22:01, 13 January 2013
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	<source lang="bash">v.to.rast input=Municipalities output=municipalities use=attr col=SHP_FID</source>		<source lang="bash">v.to.rast input=Municipalities output=municipalities use=attr col=SHP_FID</source>

	This creates a raster file called "municipalities". As vectors and raster are of different types there is little prospect of their names being confused. (Nevertheless vectors are indicated by a starting capital while rasters are kept as lowercase words.) the new raster can be seen by typing...		This creates a raster file called "municipalities". As vectors and raster are of different types there is little prospect of their names being confused. (Nevertheless vectors are indicated by a starting capital while rasters are kept as lowercase words.) the new raster can be seen by typing...

	<source lang="bash">d.rast municipalities</source>		<source lang="bash">d.rast municipalities</source>
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	<source lang="bash">r.colors map=municipalities color=random</source>		<source lang="bash">r.colors map=municipalities color=random</source>
	and {{cmd\|d.~~rast~~}} it ~~again~~.		and {{cmd\|d.redraw}} it.

	The next step requires extracting a count of the number of raster cells in each municipality. Once again this is a simple procedure. To save do this and save the output to a file called "munic_count" type...		The next step requires extracting a count of the number of raster cells in each municipality. Once again this is a simple procedure. To save do this and save the output to a file called "munic_count" type...

⚠️NikosA: improved formmating, added Category:Aggregation

2013-01-13T21:50:59Z

improved formmating, added Category:Aggregation

Show changes

⚠️NikosA: /* Method 1 */ {{cmd|r.statistics}} and minor syntactic error

2013-01-13T21:32:13Z

Method 1: {{cmd|r.statistics}} and minor syntactic error

← Older revision		Revision as of 21:32, 13 January 2013
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	''' Step 2: Convert precipitation raster to integer values '''		''' Step 2: Convert precipitation raster to integer values '''

	The tool that we will be using later, r.statistics, requires integer values. Because the precipitation raster is composed of floating point values, we have to convert it to an integer map first. In order to avoid rounding areas in the final results, we also multiply the raster by 100. This way we can divide it by 100 later in order to the original float values back.		The tool that we will be using later, {{cmd\|r.statistics}}, requires integer values. Because the precipitation raster is composed of floating point values, we have to convert it to an integer map first. In order to avoid rounding areas in the final results, we also multiply the raster by 100. This way we can divide it by 100 later in order to get the original float values back.
	If the raster that you want to aggregate into your vectors is already made of integer values or if rounding errors aren't a problem, this step can be changed or left out.		If the raster that you want to aggregate into your vectors is already made of integer values or if rounding errors aren't a problem, this step can be changed or left out.

⚠️Erget: /* Method 2 */

2012-04-11T16:18:28Z

Method 2

← Older revision		Revision as of 16:18, 11 April 2012
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	This creates a raster file called "municipalities". As vectors and raster are of different types there is little prospect of their names being confused. (Nevertheless vectors are indicated by a starting capital while rasters are kept as lowercase words.) the new raster can be seen by typing...		This creates a raster file called "municipalities". As vectors and raster are of different types there is little prospect of their names being confused. (Nevertheless vectors are indicated by a starting capital while rasters are kept as lowercase words.) the new raster can be seen by typing...

	d.rast municipalities.		d.rast municipalities

	If is looks funny change the color scheme using something like...		If is looks funny change the color scheme using something like...

⚠️Erget: /* Method 1 */

2012-01-25T12:06:25Z

Method 1

← Older revision		Revision as of 12:06, 25 January 2012
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	r.to.vect input=Precipitation_by_CatchmentArea output=Precipitation_by_CatchmentArea_Vectors feature=area		r.to.vect input=Precipitation_by_CatchmentArea output=Precipitation_by_CatchmentArea_Vectors feature=area

			In an optional last step one can combine the new vectors, which will probably not be exactly the same as the old vectors, with the old vector attribute table, either with v.db.join or v.distance using e.g. the centroids as spatial join criterium.

	=== Method 2 ===		=== Method 2 ===

⚠️MilenaN: Reverted edits by Reverse22 (talk) to last revision by Neteler

2011-12-30T21:34:54Z

Reverted edits by Reverse22 (talk) to last revision by Neteler

← Older revision		Revision as of 21:34, 30 December 2011
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	[[Category:FAQ]]		[[Category:FAQ]]
	[[Category:Vector]]		[[Category:Vector]]

	~~==Other==~~
	~~[http://thetvtopc.com/Reverse_Cell_Phone_Lookup_Number reverse phone lookup]~~

	~~[http://www.prlog.org/11289974-phone-number-lookup-verizon-phone-number-reverse-lookup-to-get-information-you-need-quickly.html phone number lookup]~~

⚠️Reverse22 at 20:57, 30 December 2011

2011-12-30T20:57:53Z

← Older revision		Revision as of 20:57, 30 December 2011
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	[[Category:FAQ]]		[[Category:FAQ]]
	[[Category:Vector]]		[[Category:Vector]]

			==Other==
			[http://thetvtopc.com/Reverse_Cell_Phone_Lookup_Number reverse phone lookup]

			[http://www.prlog.org/11289974-phone-number-lookup-verizon-phone-number-reverse-lookup-to-get-information-you-need-quickly.html phone number lookup]

Neteler at 00:31, 7 December 2011

2011-12-07T00:31:27Z

← Older revision		Revision as of 00:31, 7 December 2011
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	GIS users often wish toto aggregate the values of one polygon layer into another. Although this is not integrated as a standard tool in GRASS, it is definitely possible. This article introduces two methods to do just that: A simple, quick operation will be described that can take place entirely in GRASS GIS and produces rasters or, if desired, polygons with aggregated values from two maps and a second, more complex method that uses external editors and creates text files as outputs.		== Introduction ==

	~~'''~~Method 1:''' (written by Daniel Lee)		GIS users often wish to aggregate the values of one polygon layer into another. Although this is not integrated as a standard tool in GRASS, it is definitely possible. This article introduces two methods to do just that: A simple, quick operation will be described that can take place entirely in GRASS GIS and produces raster maps or, if desired, polygons with aggregated values from two maps and a second, more complex method that uses external editors and creates text files as outputs.

			=== Method 1 ===

			''written by Daniel Lee''

	In this example we assume that we have a vector map of catchment areas and a raster map of precipitation. We want to find out what the sum total of precipitation per catchment area is. This method would also work if the precipitation data were also stored as vector data, but the vector precipitation data would have to be turned into a raster map, just as the catchment areas are converted to rasters in the following steps. Remember to set the region, etc. in GRASS properly.		In this example we assume that we have a vector map of catchment areas and a raster map of precipitation. We want to find out what the sum total of precipitation per catchment area is. This method would also work if the precipitation data were also stored as vector data, but the vector precipitation data would have to be turned into a raster map, just as the catchment areas are converted to rasters in the following steps. Remember to set the region, etc. in GRASS properly.
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	r.to.vect input=Precipitation_by_CatchmentArea output=Precipitation_by_CatchmentArea_Vectors feature=area		r.to.vect input=Precipitation_by_CatchmentArea output=Precipitation_by_CatchmentArea_Vectors feature=area

			=== Method 2 ===

	''~~'Method 2:''' (~~written by Michael O'Donovan)		''written by Michael O'Donovan''

	GIS users accustomed to proprietary vector-based products (MapInfo, MapMaker, Atlas and some other ESRI) are often disappointed when the try migrating to OpenSource software. Many of the key functions that make vector-based systems so useful are unavailable in OpenSource software like QGIS, Thuban and GRASS. One such function is the ability to aggregate values from one polygon layer to another.		GIS users accustomed to proprietary vector-based products (MapInfo, MapMaker, Atlas and some other ESRI) are often disappointed when the try migrating to OpenSource software. Many of the key functions that make vector-based systems so useful are unavailable in OpenSource software like QGIS, Thuban and GRASS. One such function is the ability to aggregate values from one polygon layer to another.
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	# Click on to cell at the top of the first unused column and click on "Edit", "Paste special" and "unformatted text". The cells values and SHP_FID data should now be placed in the corresponding rows. Check that this has been done.		# Click on to cell at the top of the first unused column and click on "Edit", "Paste special" and "unformatted text". The cells values and SHP_FID data should now be placed in the corresponding rows. Check that this has been done.

	Variables of interest.		=== Variables of interest ===

	If you are interested in, say, aggregating populations then calculate the population per cell for every municipality. (If your data starts in row 1, population is in column C and the cell count in column K type "=C1/K1". Copy and then paste the formula into all other rows.) Give the new column an appropraite name, say, "cell_value" and save the file under its original name (i.e. as a .dbf). You may well return at a latter stage and calculate new variables of interest using the cell counts.		If you are interested in, say, aggregating populations then calculate the population per cell for every municipality. (If your data starts in row 1, population is in column C and the cell count in column K type "=C1/K1". Copy and then paste the formula into all other rows.) Give the new column an appropraite name, say, "cell_value" and save the file under its original name (i.e. as a .dbf). You may well return at a latter stage and calculate new variables of interest using the cell counts.
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	[[Category:FAQ]]		[[Category:FAQ]]
			[[Category:Vector]]

⚠️Erget at 17:52, 15 November 2011

2011-11-15T17:52:21Z

← Older revision		Revision as of 17:52, 15 November 2011
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	This procedure should already be familiar for those who work with vector maps. If vectors are not needed, it can be skipped.		This procedure should already be familiar for those who work with vector maps. If vectors are not needed, it can be skipped.

	r.to.vect input=Precipitation_by_CatchmentArea output=Precipitation_by_CatchmentArea_Vectors		r.to.vect input=Precipitation_by_CatchmentArea output=Precipitation_by_CatchmentArea_Vectors feature=area