「Plugins ftools」の版間の差分

2009年10月5日 (月) 22:33時点における最新版

fTools Plugin

The goal of the fTools python plugin is to provide a one-stop resource for many common vector-based GIS tasks, without the need for additional software, libraries, or complex workarounds. It provides a growing suite of spatial data management and analysis functions that are both fast and functional.

fTools is now automatically installed and enabled in new versions of QGIS, and as with all plugins, it can be disabled and enabled using the Plugin Manager (See Section sec:managing_plugins). When enabled, the fTools plugin adds a Tools menu to QGIS, providing functions ranging from Analysis and Research Tools to Geometry and Geoprocessing Tools, as well as several useful Data Management Tools.

fTools functions

Tables 6 through 10 list the functions available via the fTools plugin, along with a brief description of each function. For further information on an individual fTools function, please click the fTools Information menu item in the Tools menu.

表 6: fTools Analysis tools

Analysis tools available via the fTools plugin
Icon	Tool	Purpose
	Distance Matrix	Measure distances between two point layers, and output results as a) Square distance matrix, b) Linear distance matrix, or c) Summary of distances. Can limit distances to the k nearest features.
	Sum line length	Calculate the total sum of line lengths for each polygon of a polygon vector layer.
	Points in polygon	Count the number of points that occur in each polygon of an input polygon vector layer.
	List unique values	List all unique values in an input vector layer field.
	Basic statistic	Compute basic statistics (mean, std dev, N, sum, CV) on an input field.
	Nearest Neighbor analysis	Compute nearest neighbour statistics to assess the level of clustering in a point vector layer.
	Mean coordinate(s)	Compute either the normal or weighted mean center of an entire vector layer, or multiple features based on a unique ID field.
	Line intersections	Locate intersections between lines, and output results as a point shapefile. Useful for locating road or stream intersections, ignores line intersections with length > 0.

表 7: fTools Research tools

Research tools available via the fTools plugin
Icon	Tool	Purpose
	Random selection	Randomly select n number of features, or n percentage of features
	Random selection within subsets	Randomly select features within subsets based on a unique ID field.
	Random points	Generate pseudo-random points over a given input layer.
	Regular points	Generate a regular grid of points over a specified region and export them as a point shapefile.
	Vector grid	Generate a line or polygon grid based on user specified grid spacing.
	Select by location	Select features based on their location relative to another layer to form a new selection, or add or subtract from the current selection.
	Polygon from layer extent	Create a single rectangular polygon layer from the extent of an input raster or vector layer.

表 8: fTools Geoprocessing tools

Geoprocessing tools available via the fTools plugin
Icon	Tool	Purpose
	Convex hull(s)	Create minimum convex hull(s) for an input layer, or based on an ID field.
	Buffer(s)	Create buffer(s) around features based on distance, or distance field.
	Intersect	Overlay layers such that output contains areas where both layers intersect.
	Union	Overlay layers such that output contains intersecting and non-intersecting areas.
	Symetrical difference	Overlay layers such that output contains those areas of the input and difference layers that do not intersect.
	Clip	Overlay layers such that output contains areas that intersect the clip layer.
	Difference	Overlay layers such that output contains areas not intersecting the clip layer.
	Dissolve	Merge features based on input field. All features with indentical input values are combined to form one single feature.

表 9: fTools Geometry tools

Geometry tools available via the fTools plugin
Icon	Tool	Purpose
	Check geometry	Check polygons for intersections, closed-holes, and fix node ordering.
	Export/Add geometry columns	Add vector layer geometry info to point (XCOORD, YCOORD), line (LENGTH), or polygon (AREA, PERIMETER) layer.
	Polygon centroids	Calculate the true centroids for each polygon in an input polygon layer.
	Delaunay triangulation	Calculate and output (as polygons) the delaunay triangulation of an input point vector layer.
	Simplify geometry	Generalise lines or polygons with a modified Douglas-Peucker algorithm.
	Multipart to singleparts	Convert multipart features to multiple singlepart features. Creates simple polygons and lines.
	Singleparts to multipart	Merge multiple features to a single multipart feature based on a unique ID field.
	Polygons to lines	Convert polygons to lines, multipart polygons to multiple singlepart lines.
	Extract nodes	Extract nodes from line and polygon layers and output them as points.

表 10: fTools Data management tools

Data management tools available via the fTools plugin
Icon	Tool	Purpose
	Export to projection	Project features to new CRS and export as new shapefile.
	Define projection	Specify the CRS for shapefiles whose CRS has not been defined.
	Join attributes	Join additional attributes to vector layer attribute table and output results to a new shapefile. Additional attributes can be from a vector layer or stand-alone dbf table.
	Join attributes by location	Join additional attributes to vector layer based on spatial relationship. Attributes from one vector layer are appended to the attribute table of another layer and exported as a shapefile
	Split vector layer	Split input layer into multiple separate layers based on input field.