Tagged Questions

Statistical computing language and software environment.

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5
votes
1answer
162 views

Spatial graphing, distribution of polygon area over latitudes

Given a polygon in a PostGIS database, what is the best way to create a graph of its distribution over a range of latitudes? I'm picturing a graph of a curve, where the proportion of the total area ...
13
votes
1answer
683 views

Robust alternatives to Moran's I

Moran’s I, a measure of spatial autocorrelation, is not a particularly robust statistic (it can be sensitive to skewed distributions of the spatial data attributes). What are some more robust ...
3
votes
1answer
280 views

Where can I download a xyz bathymetry file of the Northwest Atlantic?

I'm looking to download the bathymetry of the Northwest Atlantic ocean as a txt file or any other file format that I can easily upload and use in R. I once used the Global topography - Scripps ...
4
votes
2answers
419 views

QGIS affine - form of equation

I am at the mercy of a govt authority who have provided utility information in a cad format with a 0,0 origin and a nonsense grid. About a dozen files, the grid and origin are entirely arbitrary. To ...
3
votes
1answer
831 views

How to intersect lines and polygons in R?

Following on from an answer about intersecting polygons with lines to chop up a polygon into smaller polygon units (in QGIS), I wanted to try the same thing in R. However, I cannot seem to find a ...
4
votes
2answers
654 views

Create a raster with georeferenced information in R

Referring to my previous question, how do I "geocode"/convert - using R - a generated raster image to a format that can be shown as a layer on a map? In short, I'm aiming to recreate the results of ...
4
votes
4answers
1k views

How to split a vector in equal smaller parts in QGIS or similar?

i want to divide a shapefile with many tiles into a lot of smaller tiles. I am searching for a smart solution, because manual edits are out of questions Anyone can help or know a nice function?
9
votes
5answers
2k views

Get Raster Values from a Polygon Overlay in Opensource GIS Solutions

I have two layers. A polygon-shape-layer with many tiles and a raster-layer containing CORINE 2006 land cover with many categories in a colourmap. I want to obtain for each polygon in the shapelayer a ...
1
vote
1answer
173 views

Get raster field names in R

Does anyone know how I can extract the raster field names (VALUE, COUNT and other existing field names on a categorical raster file) in R? I am using the raster package to load the raster files.
1
vote
0answers
214 views

How to extract polygon means from raster data and match the mean to the original attributes from the shapefile? [closed]

My polygons (p) was read from a shapefile (shp). I know that I can extract the polygon means by: means <- extract (r, p, fun="mean") My question is how I can match each mean with the ...
1
vote
2answers
103 views

Looking for R-compatible geospatial datasets

I try to work with geospatial data of North America. Is there any high-resolution map material available for/in R?
4
votes
2answers
560 views

How to draw a point at an exact location with spplot?

I imported a Shapefile holding a quite detailed world map from: http://www.diva-gis.org library(sp) library(rgdal) world = readOGR('./countries_shp/', 'countries') Using R with the sp-Packages, ...
2
votes
3answers
778 views

How to extract the US from a North America Shapefile?

I have a north america shapefile, downloaded from ftp://ftp.epa.gov/wed/ecoregions/cec_na/NA_CEC_Eco_Level2.zip How can I get a new shapefile from this showing only us? Is there a way doing this in ...
2
votes
1answer
1k views

How to convert decimal degrees units to km in R?

I am trying to figure out how I can transform my unit of length from decimal degree to km when I import the following simple ArcGIS polygon shape. Ultimately, I would like to have this information ...
4
votes
0answers
401 views

How to get rpy2 for QGIS on OSX?

I am a new QGIS user, have installed QGIS on a Mac running Snow Leopard OSX 10.6.8 following all the instructions. QGIS seems to work well for everything other than when I boot up I get the message ...
1
vote
0answers
150 views

How to load big ASCII rasters in Revolution R?

Is there anyone in this site using Revolution R with big spatial data ? I am trying to load raster files (ascii format) into revolution r using the xdf format, with no luck. Did anyone tried this ...
2
votes
2answers
497 views

Create a ground overlay kml from georeferenced raster

I have a world georeferenced raster (5m resolution, ~4000 x 4000 pixels) that I would like to display in google earth. I am looking for a simple and effective way to generate this kml file. Using ...
0
votes
0answers
108 views

Making a Bridge Classification tool in GRASS GIS

I'm working on a tool for classifying bridges with GRASS. I have been using examples online but I've come to a standstill as how to actually make this tool in GRASS. I have my raster of my area and ...
1
vote
0answers
239 views

How do I implement 'weighted' kriging in R?

I'm trying to interpolate the values of an attribute (called "disease_rate") that i've sampled at a set of spatial points and i'd like to add 'weights' to the resulting kriging estimates. Basically, ...
2
votes
2answers
330 views

ArcGIS Desktop 10 ModelBuilder iterations

Hi all I have some home range estimates for fish that I made using the adehabitat pkg in R. However, a lot of them overlap land, so I need to subtract the area where they overlap with land ...
6
votes
1answer
2k views

GIS, R and shapefiles

I have some data that encodes locations in certain countries, such as the US and China, that I would like to map. The data includes location name in Latin, extended Latin and other scripts (Japanese, ...
2
votes
1answer
476 views

Conversion of raster features to polylines: skeletonization?

I would like to identify linear features, such as roads and rivers, on raster maps and convert them to a linear vector features (i.e. polylines). I typically use R as my primary GIS, and have posed ...
1
vote
1answer
800 views

merging 2 polygon adjacent to each other using R

I have several shp files which are the components (or tiles) of a map, I have joint all these tiles together to have a large shp file. Then I realized some of the polygon is now splitted into 2 ...
2
votes
2answers
139 views

Color a layer of the map based on the location of dots on another layer

Thanks for helping me in GIS 101 Problem #2, now I have followup questions: I created a map as below: The map is created using the following script: ct <- ...
4
votes
1answer
1k views

How to plot points on maps using ggplot2 and R?

Thanks for help me in GIS 101 Problem #1, now I have geocoded a few hospital in Connecticut using google map, I have able to visualize them in QGIS, now I am trying to do it in R. ct <- ...
9
votes
1answer
222 views

How to find the most spread out locations?

Probably a very simple question. I have a list of about a thousand potential geographical locations (lat lon), and of those I need to select the 200 locations that are "most spread out". I think that ...
3
votes
1answer
250 views

Spatial Interpolation Methods like PRISM

I am looking for some kind of software (free software) that allows me to make an interpolation like PRISM software. The interpolation used in PRISM is a local regression and accounts for ...
6
votes
3answers
397 views

Identification of consecutive points within a specified buffer

I have a point file, hourly relocations of an animal, and I want to be able to place a buffer around each point and calculate the number of subsequent points which are within the buffer zone. I am ...
2
votes
1answer
514 views

How to select a Subset of PolySet data in R?

I am using the PBSmapping package in R to model data from diva-gis. I can read in the shapefiles and plot them with no issue. library(PBSmapping) df = importShapefile("/path/df.shp") plotPolys(df) ...
2
votes
1answer
886 views

Converting NZMG (or NZTM) to latitude / longitude for use with R map library

I am a statistician with no background in GIS so apologies for the newbie question. We routinely use R for a range of statistical and graphic analysis and are interested in using its map library to ...
2
votes
1answer
175 views

Generic comparison for kriging in geoR and ArcGIS

I am going to do a project based on kriging. The targeted area would be as big as United States and my grid would be 10km*10km. I am wondering the differences of efficiencies for the methods ...
6
votes
2answers
539 views

creating a raster of the residuals of a regression between two rasters

I am trying to create a raster of the residuals of a regression between two rasters. i.e. I would like to carry out a regression of one raster against another of the same extent and plot the residual ...
2
votes
2answers
1k views

How to overlay map layers (shp and csv) in R?

This is a crosspost from stackoverflow. I know very little about GIS software and am doing all my mapping in R. Apologies in advance if this is too basic question. Let's say I have two shapefiles from ...
10
votes
1answer
2k views

How can I convert data in the form of lat, lon, value into a raster file using R?

I have a data set of values over a km grid in the continental U.S. The columns are "latitude", "longitude", and "observation", e.g.: "lat" "lon" "yield" 25.567 -120.347 3.6 25.832 ...
1
vote
2answers
262 views

NA values in dbf when exporting shapefile from R with writeOGR?

I´m writing an esri shapefile from R (2.14.1) on windows, using writeOGR in the rgdal package, in the resulting dbf file, NA values in the spatialpointdataframe (in numeric columns) are not translated ...
1
vote
0answers
255 views

Administrative level and coordinates from Yahoo GeoPlanet WOEID

The Yahoo GeoPlanet data can be freely downloaded from: http://developer.yahoo.com/geo/geoplanet/data/. If I understand it correctly, each WOEID corresponds to a unique location on earth, with ...
3
votes
1answer
90 views

How to determine if feature A and B are located in the same room?

I have created a map using MapWindows like the following: A little explanation here, the is a map of an elderly home. The yellow boxes are room and the white rectangles inside the yellow boxes are ...
9
votes
2answers
798 views

How to get the second nearest neighbor between two point patterns in R?

Is there a way to get the distances for the second nearest neighbor between two point patterns in R? The spatstat package has a function called nncross but it only applies to the nearest neighbors ...
14
votes
1answer
530 views

Monte Carlo simulation using QGIS and pgRouting on optimal sidewalk construction

I am new to spatial analysis and would appreciate some general direction on a project I am attempting, outlined below (I am starting from scratch). GOAL: To find the best locations to install 2000 ...
13
votes
4answers
4k views

How to open a Shapefile in R?

I need to open a shape file from ArcMap in R to use it for further geostatical analysis. I've converted it into ASCII text file, but in R it is recognized as data.frame. Coordinates function doesn't ...
4
votes
3answers
625 views

How can I find out how to convert this point to lat lon?

I have received a shapefile with measurement points to be analyzed, but no matter how I try, I can't find how to convert to lat lon. I suppose it would be good to know the projection but when I look ...
4
votes
1answer
1k views

Spatial distance join between polygon and points using R?

I'm figuring out how to do a Intersection (Spatial Join) between point and polygons from shapefiles. My idea is to get the closest points and those points that match completely inside the polygons. In ...
7
votes
1answer
1k views

Instantiating spatial polygon without using a shape file in R

So, the usual way we read a shapefile in R is via the maptools package, like this: sfdata <- readShapeSpatial("/path/to/my/shapefile.shp", proj4string=CRS("+proj=longlat")) However, I have a use ...
0
votes
1answer
540 views

dependency ‘stringr’ is not available for package ‘rgeos’

Attempting to install rgeos package fails. Detailed error logs as follows:- > install.packages("rgeos", repos="http://R-Forge.R-project.org") Installing package(s) into ...
4
votes
1answer
92 views

Is it possible to use RPy/RPy2 in a Geoprocessing Script that is exposed as a GP Task on ArcGIS Server?

Is it possible to publish a Script tool that uses the RPy/RPy2 module (or more generally any Python-to-R link) to ArcGIS Server 10 SP2? If so, what specifically do I need to do, i.e. Install R on the ...
4
votes
1answer
2k views

Converting a polygon into a raster using R

I'm trying to convert a shapefile into a raster within R. My approach is to read in the raster as follows: library(rgdal) # Loads SP package by default demo <- readOGR('F:/data/', 'shapefile') # ...
10
votes
3answers
2k views

How to cluster spatial data in R?

I am very new to R, so please bear with me : > I have bunch of data points with latitude and longitude. I want to use R to cluster them based on their distance. I have already taken a look at this ...
4
votes
1answer
483 views

Superimpose grid on points, then aggregate points within each grid cell

I have a vector of presence/absence values (1,0) and a matrix of x,y coordinate data (projected) specifying the spatial position of each value (about 25,000 in total). I'd like to aggregate the point ...
7
votes
1answer
1k views

Raster legend in R: how to colour specific values?

I have an elevation model plotted in R r <- raster("example.dem") plot(r, col = topo.colors(20)) Some of the values are below sea level (0), and I'd like to have those display in red. How can ...
10
votes
1answer
541 views

Random sampling of raster using R

Is there a straightforward way of randomly sampling a raster so that the output of the process is a raster? I'm using an example that I found on the r-sig-geo list and I have also tried the ...

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