How to create spatial polygons in your using shapefile?

How to create spatial polygons in your using shapefile?

The shapefile function in the raster package is very convenient in that it can both read a shapefile into R but it can also write a SpatialPolygons or other spatial object classes (lines, polygons, etc.) to a shapefile. Creating 100s of polygons by hand is a very daunting task.

How to create a spatial polygon layer from scratch?

Let’s begin by creating a set spatial polygons layer from scratch. We’ll use the sp package to make a SpatialPolygons object. First we need to create a set of XY coordinates that represent the vertices of a polygon. We’ll use use some randomly generated XY coordinates.

Can you dissolve state boundaries into one polygon?

We can get around that by dissolving boundaries based on similar attributes. Essentially collapsing multiple polygons into a single polygon. Here we’re going to dissolve the state boundaries to make a single United States (lower 48) border polygon.

What’s the difference between spatial and spatialpolygonsdataframe?

The difference between SpatialPolygons and SpatialPolygonsDataFrame are the attributes that are associated with the polygons. SpatialPolygonsDataFrames have additional information associated with the polygon (e.g., site, year, individual, etc.) while SpatialPolygons contain only the spatial information (vertices) about the polygon.

Is there a spatial join function in ArcGIS?

There is a spatial join function both in the toolbox and in the main interface; the toolbox version gives you a bit more control as to how to perform the join, and how large a radius to consider for each match. I use that if it is a large dataset, i.e. more than a few 1000 points for performance reasons.

How do you join two polygons in ArcGIS?

The 2 polygons are simple non contiguous parcels of land that need to be treated as one parcel. In desktop help, I found the following instructions (I could not find any other reference to joining polygons): “Select the polygon graphics on the map you want to join.

How to create a spatialpolygonsdataframe from a list?

In the following there´s an example of a list of Polygons from which a SpatialPolygonsDataFrame, containing all Polygons of the list, should be created. EDIT: The SpatialPolygonsDataFrame must be created from the list of SpatialPolygons!

What’s the difference between spatial and spatial polygons?

SpatialPolygonsDataFrames have additional information associated with the polygon (e.g., site, year, individual, etc.) while SpatialPolygons contain only the spatial information (vertices) about the polygon. Let’s begin by creating a set spatial polygons layer from scratch.

How to join polygons in R-Geographic Information Systems?

The following solution is based on a post by Roger Bivand on R-sig-Geo. I took his example replacing the German shapefile with some census data from Oregon you can download from here (take all shapefile components from ‘Oregon counties and census data’).

What are the vertices of a spatial polygon?

Spatial polygons are a set of spatially explicit shapes/polygons that represent a geographic location. Spatial polygons are composed of vertices which are a set of a series of x and y coordinates or Spatial points. Spatial polygons can be combined with data frames to create what’s called a SpatialPolygonsDataFrame.

How are polygons aggregated in a geographic information system?

See the image below, black borders indicate the original polygons, whereas red borders represent polygons aggregated by oregon.id. So far, so good. However, data attributes related to the original shapefile’s subregions (e.g. population density, area, etc.) get lost when performing unionSpatialPolygons.

How to plot multiple shapefiles in base R?

This tutorial builds upon the previous tutorial , to work with shapefile attributes in R and explores how to plot multiple shapefiles using base R graphics. It then covers how to create a custom legend with colors and symbols that match your plot. Plot multiple shapefiles using base R graphics.

How to work with vector data in R?

To work with vector data in R, we can use the rgdal library. The raster package also allows us to explore metadata using similar commands for both raster and vector files. We will import three shapefiles. The first is our AOI or area of interest boundary polygon that we worked with in Open and Plot Shapefiles in R .

How to create a CSV file with polygons?

I am going to have a csv file which has the lat/long of the vertexes of the polygons and some of the polygon areas will be square (and have four vertexes), however some of the polygons will have more complex shapes and may have 10 or more vertexes.

How to read and write shapefiles with R?

It is important to know how to work with shapefiles in R to access incredible functionality and analytic ability–much of which is unavailable in many GIS software packages. Of course, working with spatial data in an open source environment is always good!

Where are the shapefiles stored in nhsboards object?

Notice that we have 5 “slots” stored in NHSBoards object, namely @data, @polygons, @plotOrder, @bbox and proj4string. These slots can be accessed using @ and the first two are the main interest here. You can think of the @data slot as a table that stores attribute data pertaining to the geographic area of interest.

Is there such a thing as a shapefile?

Once you have found and downloaded the Shapefiles you are interested in, they typically come as a zip file, we can get going. As the very existence of the zip file possibly alludes to, a “Shapefile” isn’t actually a single file but a collection of files.