similar to: calculate area between intersecting polygons

Hi, my doubt is very simple. I'm sure I've seen someone using something like this before, but unfortunatelly my searches in the archives were useless. Well, I have some objects called after a name that has a number attached to it, varying. Let's say I have: > ls poly1 poly2 poly3 poly4 poly5 poly6 ... I would like to access these objects using a for(), in which I could do

Dear all, 1. How can I compute the intersecting area between 2 polygons ? 2. I have polygons with coordinates in decimal degrees (i.e. 13 deg 30 min = 13.5 decimal degrees). I want to compute their area and get the results in square meters or square kiometers. Can anyone give me a conversion coefficient or a pointer where I can find this information (sorry for this off topic question) ? Thanks

Dear R-helpers, thanks for yesterday's speeding-up tip. Here is my next query: I have lots of polygons (not necessarily convex ones, and they never have holes) given by x,y coordinates. I want to get the polygon that is the union of these polygons. This is my current method, but I am hoping there is a faster method (up to thousands of polygons, each with ca. 40 xy points). Example:

I am a new user of the R spatstat package and am having problems creating a polygonal observation window with owin(). Code follows: library("maps") library ("sp")` library("spatstat") mass.map <- map("state", "massachusetts:main", fill=T) # This returns a data frame includding x and y components that form a polygon of massachusetts mainland`

Imagine that I have a large number of points (given by coordinates x and y) that vary in density per space. For the purpose of demonstration it could be generated like this: s <- data.frame(x=runif(10000,0,900),y=runif(10000,0,900)); plot(s) I want to create polygons around the points where point density is greater than a selected threshold (for example, by using krieging or equivalent

Hi everyone. I have these data: probClass<-seq(0,0.9,0.1) prob1<-c(0.0070,0.0911,0.1973,0.2949,0.3936,0.5030,0.5985,0.6869,0.7820,0.8822) prob2<-c(0.0066,0.0791,0.2358,0.3478,0.3714,0.3860,0.6667,0.6400,0.7000,1.0000) # which I'm plotting as follows: plot(probClass,prob1,xlim=c(0,1),ylim=c(0,1),xaxs='i',yaxs='i',type="n") lines(probClass,prob1)

Dear R-users, Is there any way of calculating the perimeter of a polygon in a shapefile object? Furthermore, how to calculate the length of the common border of two polygons? I've searched the code of spded, but could not find a hint on how to do it. Thank you very much, Leo. [[alternative HTML version deleted]]

Hello, I need to calculate the centroids of some spatial polygons that I have placed into a Polygons-class object. Is the labeling point in the Polygons-class the centroid of the polygon? Thank you for your help.

Hi all, Given a number of points (x,y) in a plane, I'd like to plot a map of polygons, so that 1) each polygon contains exactly one point 2) the polygon defines the area for which this specific point is closer than any other point. It's a bit like a map of areas "influenced" by that point, and it's obviously a matter of intersecting the perpendicular bisectors

Hello! I''m releasing an extraction from an application I''m currently working on. It''s a small library for dealing with points and polygons, called Polygons. It really just implements some textbook algorithms w/ Prototype-style JavaScript classes. Check it out here: http://polygons.mdaines.com/ The demo on that page (Firefox/Safari only right now) uses the

Dear all, Does anyone know of a function that calculates the area of the outer polygon constructed from a data frame with co-ordinates? For example, library(splancs) test = rbind(c(0,0), c(10,0),c(10,10),c(0,20)) plot(test) areapl(test) [1] 150 This is OK, but I want the same area to be returned (150) when adding yet another co-ordinate in the middle of the polygon: test = rbind(c(0,0),

Hello, I have a distribution dataset for species consisting of xy coordinates at the 1km resolution, with only presence data. So a simplified example of a species distribution might be: y <- rbind(as.integer(rnorm(100,50,20)), as.integer(rnorm(200,100,30)), as.integer(rnorm(100,180,15))) x <- rbind(as.integer(rnorm(200,50,20)), as.integer(rnorm(200,100,20)), as.integer(rnorm(100,200,15)))

Hello: I would like to superimpose vector polygons (state outlines) from a Shape file on top of a satellite image, imported into a SpatialGridDataFrame from GEOTIFF via gdal_translate and readGDAL. When I plot polygon and point shape files in R, into SpatialPointDataFrame and SpatialPolygonDataFrame, the two feature sets line up geographically, so it seems logical that a SpatialGridDataFrame

Does anyone have any experience plotting complex polygons on a scatterplot3d display? I would like to present some spatially binned data in a 3-d type plot with background polygons (i.e.. a filled coastline map). I can get the coastline onto the plot window as a line type but cannot figure out how to fill the shape. I'm certain it may be possible but might require a bit of digging

Hello, I'm verry new in R. My Problem: I have a PostgreSQL-Server with installed support for the R-Language. And now I have a table with a Polygon like this: test_db=# select * from geo where id=1; id | koerper ----+--------------------------------- 1 | ((0,0),(0,2),(2,2),(3,3),(5,0)) (1 row) Now, I need to know the area of this object. Please, can you tell me, if it

Dear R-Helpers, Is there a way to draw shaded (filled) polygons in panel graphs produced by xyplot ? I made different trials (see below) with polygon() and grid.polygon() but polygons are not drawn (probably for the same reason that prevents the use of lines, points, etc. in xyplot panels). Thanks in advance, Renaud > Water id label longitude latitude 515 21 Zone inondable

Hi, I'm looking the best way to fill irregular polygons with patterns, Something like the function grid.pattern do, but my case is with irregular polygons. Whit this script I can get it, but I'm looking for an "elegant" solution.. library(grid) grid.polygon(x=c(0.2, 0.8, 0.6, 0.6, 0.8, 0.2), y=c(0.2, 0.2, 0.3, 0.5, 0.7,0.7), gp=gpar(fill="grey",

I was just thinking last night, how about this: For each frame, detect edges and divide the frame into a bunch of non-overlapping polygons. Extract textures from the first frame, then save changes in polygon vertex coordinates only, unless the textures change too much in which case new textures (which could be wavelet compressed) would be stored. Also, if the movements of the vertices would

Dear all, I had to place points at random, one in each of larger number of polygons (actually in objects of class 'SpatialPolygonsDataFrame' , see sp library), and tried first to do it using spsample (from sp). Surprisingly, every 5-15 trials, the output was a NULL value. The doc says that ' this may occur when trying to hit a small and awkwardly shaped polygon in a large

Sorry, I did not make my question clear. Since I have a point theme with many points, some of them may clump together. the problems here are: 1. how to find clumps in a point theme? 2. the convex-hull extension I found only deal with all the points in a theme at each time? how to make each convex hull around each point clump automatically? Thanks. Xiaohua On 5/12/06, Bob Booth <bbooth