Plugins ftools

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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
Matrix.png 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 lines.png Sum line length Calculate the total sum of line lengths for each polygon of a polygon vector layer.
Sum points.png Points in polygon Count

the number of points that occur in each polygon of an input polygon vector

Unique.png List unique values List all unique values in an input vector layer field.
Basic statistics.png Basic statistic Compute basic statistics (mean, std dev, N, sum, CV) on an input field.
Neighbour.png Nearest Neighbor analysis Compute nearest neighbour statistics to assess the level of clustering in a point vector layer.
Mean.png 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.
Intersections.png 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.png Random selection Randomly select n number of features, or n percentage of features
Sub selection.png Random selection within subsets Randomly select features within subsets based on a unique ID field.
Random points.png Random points Generate pseudo-random points over a given input layer.
Regular points.png Regular points Generate a regular grid of points over a specified region and export them as a point shapefile.
Vector grid.png Vector grid Generate a line or polygon grid based on user specified grid spacing.
Select location.png 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.
Layer extent.png 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.png Convex hull(s) Create minimum convex hull(s) for an input layer, or based on an ID field.
Buffer.png Buffer(s) Create buffer(s) around features based on distance, or distance field.
Intersect.png Intersect Overlay layers such that output contains areas where both layers intersect.
Union.png Union Overlay layers such that output contains intersecting and non-intersecting areas.
Sym difference.png Symetrical difference

Overlay layers such that output contains those areas of the input and

difference layers that do not intersect.
Clip.png Clip Overlay layers such that output contains areas that intersect the clip layer.
Difference.png Difference Overlay layers such that output contains areas not intersecting the clip layer.
Dissolve.png 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.png Check geometry Check polygons for intersections, closed-holes, and fix node ordering.
Export geometry.png Export/Add geometry columns Add vector layer geometry info to point (XCOORD, YCOORD), line (LENGTH), or polygon (AREA, PERIMETER) layer.
Centroids.png Polygon centroids Calculate the true centroids for each polygon in an input polygon layer.
Delaunay.png Delaunay triangulation Calculate and output (as polygons) the delaunay triangulation of an input point vector layer.
Simplify.png Simplify geometry Generalise lines or polygons with a modified Douglas-Peucker algorithm.
Multi to single.png Multipart to singleparts Convert multipart features to multiple singlepart features. Creates simple polygons and lines.
Single to multi.png Singleparts to multipart Merge multiple features to a single multipart feature based on a unique ID field.
To lines.png Polygons to lines Convert polygons to lines, multipart polygons to multiple singlepart lines.
Extract nodes.png 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 projection.png Export to projection Project features to new CRS and export as new shapefile.
Define projection.png Define projection Specify the CRS for shapefiles whose CRS has not been defined.
Join attributes.png 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 location.png 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 layer.png Split vector layer Split input layer into multiple separate layers based on input field.