Statistical computing language and software environment.

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14
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4answers
6k 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 ...
7
votes
1answer
1k views

use proj4 to specify Robinson projection with R ggmap and ggplot2 packages?

I want to project this map in robinson projection: library(ggmap) world <- map_data("world") ggplot() + geom_path(data = world, aes(long, lat, group = group)) ...
10
votes
1answer
4k 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
4answers
1k views

Problems with NA values when reading .DEM file with R 'raster' package in Windows

I am trying to read a raster file in a .DEM format on windows using the 'raster' package in R. I get problems with NA values, when loading the data into R in Windows 7, but I do not have the problem ...
8
votes
1answer
1k views

How can I use fortify() to create a filtered R data frame from a shape file?

I am in the process of building a ggplot choropleth map of population in administrative areas in Wales. I have downloaded the Boundary-Line data from the Ordnance Survey and extracted what seems to be ...
4
votes
1answer
647 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, ...
10
votes
2answers
262 views

Count raster value in a bounding box (spatial extent)

I have simple question: given a bounding box, how can I count the number of specific values (say, I am interested in the number of value == 1 ) in a raster in 1) arcpy, or 2) raster package in R?
9
votes
1answer
281 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 ...
8
votes
3answers
295 views

R, rasterVis and RGL: how to prevent reflective surfaces?

I have been experimenting with digital terrain model files in ESRI ASCII grid raster format. Despite zero experience with this type of data I found it very easy to load into R, as per code below. The ...
7
votes
1answer
13k views

find the centroid of a cluster of points

While searching the web, solutions for finding centroids of polygons come up rather often. What I'm interested in is finding a centroid of a cluster of points. A weighted mean of sorts. I would ...
3
votes
2answers
3k views

Choosing the correct value for proj4string for shape file reading in R “MapTools”

I am having a shape file of polygons and another CSV file which contains a list of points as (Lat, Lng) pairs.. I want to check for each (lat, lng) pair from the CSV file which polygon does it fall ...
11
votes
2answers
3k views

How to efficiently read a kml file into R

Hi I'm working with huge .kml files (up to 10 Gb) and need an efficient way to read them into R. Until now I've been converting them to shapefiles via QGIS and then back into R with readShapePoly and ...
11
votes
5answers
5k views

How best to fix a non-noded intersection problem in PostGIS?

I'm using a PL/R function and PostGIS to generate voronoi polygons around a set of points. The function that I am using is defined here. When I use this function on a particular dataset I get the ...
7
votes
2answers
890 views

Is it possible to run an R script on a layer in QGIS?

I'd like to run an R script on a layer loaded in QGIS (to rotate a set of points created there using the Vector:Research Tools:Regular Points tool). I thought ManageR might work but cannot get it ...
6
votes
1answer
4k views

R : convert a spatial polygon objet to spatial polygon data frame

My goal is to modify an existing shapefile by merging certain polygons. After importing the shapefile and using the UnionSpatialPolygons command, I get the polygon outline that I want. However, this ...
6
votes
3answers
2k views

How to efficiently read and reclassify many rasters in R

I've been tasked to create a suitability analysis of wave conditions in the Gulf of Mexico. I have 2 thousand or so raster files that are about 8 MB each (2438 columns, 1749 rows, 1km cell size). ...
5
votes
4answers
3k views

how to overlay a polygon over SpatialPointsDataFrame and preserving the SPDF data?

I have a SpatialPointsDataFrame with some additional data. I would like to extract those points inside a polygon and at the same time, preserve SPDF object and its corresponding data. So far I've ...
1
vote
4answers
260 views

Detection of geographical trend of a variable

What is the best method to detect and graphically display the spatial trend of a variable? I'm looking for something that tells me the probability that the trend is from "north-west to south-east" or ...
10
votes
2answers
2k views

Aggregating points to grid using R

I have a question with regard to spatial aggregation in R. What I am trying to do is aggregate a point dataset to a grid. I am unsure however how to do this as I have little experience with this sort ...
9
votes
4answers
6k views

How can I export raster data from Arcmap to an R *.grd file format?

I want to work with raster data in R, but I have problems exporting my raster dataset from ArcMap. By "export data"/GRID I get a file with an *.aux extension. What I need is *.grd. Can anybody help ...
8
votes
3answers
653 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 ...
8
votes
3answers
2k views

R: Download a large DEM, change projection, and adjust to smaller scale

This is a process that takes just a few seconds in GIS software. My attempt to do it in R uses a large amount of memory then fails. Is there something wrong in my code, or is this just something R ...
7
votes
5answers
3k views

Calculate distance in km to nearest points (given in lat/long) using ArcGIS DEsktop and/or R?

I have two point datasets in ArcGIS, both of which are given in WGS84 lat/lon co-ordinates and the points are spread across the whole world. I would like to find the nearest point in Dataset A to each ...
4
votes
1answer
696 views

Self organizing maps and spatially Constrained Clustering in R

There are a few algorithms to perform spatial clustering in R but most of them focus on point pattern analysis (for example here). I would like to perform spatial constrained clustering for polygon ...
4
votes
1answer
1k views

How to re-project ease( Equal Area Scalable Earth) grid with a ~25 km cylindrical projection to WGS84 0.25 degree? [duplicate]

I have nc (NetCDF) files for global soil moisture. From the metadata, the projection is cylindrical and the resolution is 25 km (it is based on authalic sphere based on International 1924 ...
4
votes
1answer
3k 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 <- ...
3
votes
1answer
110 views

problem with polygon smoothing in R

With R I am looking to smooth my Polygon: inter2.csv code: inter1 <- read.table("c:/inter2.csv", header=TRUE) # add a category (required for later rasterizing/polygonizing) inter1 <- ...
3
votes
1answer
130 views

Spatial Classification

I am not sure what to call my problem. From this image, I have a set of classified polygons (colored). I would like a way to classify the white polygons in the image. I don’t have any attributes to ...
3
votes
1answer
440 views

How do I create a heatmap in ggplot?

I'm using R with ggplot2 to generate maps from shapefiles and from data in SQL Server. I'm trying to get to a stage where I can automate a large chunk of the mapping I do. So far this is working well ...
3
votes
1answer
323 views

How to speed up band math in R 'raster' package?

I have some GeoTiff rasters with over 100 bands in total, but they are not huge: resolution is about 1200x600 and total size is less than 7 mb. I'm trying to do a simple NDVI calculation: raster ...
3
votes
2answers
2k 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
85 views

Are there examples of high-level interfaces to NetCDF

The R raster package and GDAL both have independent wrappers around NetCDF-4* that treat an array variable as a "complete" dataset, i.e. they provide objects or interfaces that seamlessly give access ...
2
votes
1answer
297 views

Bubble Plots in R not displaying

I was attempting to follow a tutorial to create a bubble plot of school district proficiency rates. Data shapefile of school districts (Census2010.shp) ...
2
votes
1answer
2k views

joining polygons

I am wondering how to join spatial polygons using R code ? I'm working with census data where certain areas change over time and I wish to join the polygons and the corresponding data and simply ...
6
votes
2answers
974 views

Convert several SpatialPointsDataFrames to raster

There are 100 SpatialPointsDataFrames in my Workspace. I loaded them on this way: filenames <- list.files(path="", pattern="XYhectareTravelTimes_ez+.*shp") for(i in ...
5
votes
1answer
305 views

Why does ManageR and rpy2 not work in QGIS (1.8.0-Lisboa)?

I have been trying to get R scripts to function and ManageR to work within QGIS (1.8.0-Lisboa). (Windows 7). Python2.7.5. Two problems indicated that R was not working in QGis. First - when I run an ...
5
votes
1answer
413 views

Rgeos drops associated values when intersecting polygons

I am trying to intersect two SpatialPolygonsDataFrames and get a SpatialPolygonsDataFrame as the result. Unfortunately, using the gIntersection function from rgeos (which works impressively quickly ...
5
votes
3answers
331 views

Create Zonal Grid in R

Suppose I have a n*n raster, and I want to create k square blocks (k can be divided exactly by n*n ) for zonal analysis: for example, when n = 4 and k = 4 a 4*4 raster is create with value 1 1 2 2 ...
4
votes
1answer
224 views

How to 'reverse clip' (erase) in R

A reverse clip saves only the part of your spatial object that is outside the bounds of another object, as opposed to a regular clip which saves the parts that are inside the other object. Here's how ...
4
votes
0answers
438 views

Using stat_density2d with coord_map in ggplot2

In my example I am plotting a shapefile for all England & Wales, however I'm interested in the greater London area. If I allow ggplot to simply default and display the entire shapefile then the ...
4
votes
1answer
217 views

How to create cohesive Spatial Pixels from Spatial Points Dataset

I have a Spatial Point DF spo (covering an irregular shaped area of interest). The data are not on a regular grid due to crs transformation. My goal is a raster with predefined resolution and extent ...
3
votes
1answer
86 views

How to create randomly points within polygons for each row of a dataframe matching a Polygon ID with R

My question is similar to this post, but because there are no "perfect" answer and above all no reproducible example I open this question. I have a "SpatialPolygonsDataFrame" and a data frame. Both ...
3
votes
3answers
573 views

Convert 800 .hdf4 files to Tiff using GRASS/QGIS/SAGA/GDAL/R

I've have MODIS ndvi data (MODIS_Grid_16 days NDVI) from the iberian peninsula, from February of 2000 to August of 2012 (really big data). How do I batch convert about 800 .hdf MODIS files to .tif ? ...
3
votes
3answers
1k 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 ...
3
votes
1answer
3k views

Convert a shapefile with northing/easting to ASCII raster with latitude/longitude

Linked below is a polygon shapefile whose projection is NAD83 and whose values are LU/LC codes. Coordinates are meters of northing and easting. I would like to convert it to an ASCII raster with ...
2
votes
1answer
134 views

Count overlapping polygons in single shape file with R

I have a shapefile of species ranges for ~ 346 species. Some species have multiple polygon ranges so there are 1,078 polygons and many polygons are multi-part. It looks something like this: I ...
2
votes
2answers
150 views

Wrong projection high quality shapefile for the coastline of Helsinki region (Finland)

I did some spatial interpolations in R and I need a support for those. Looking for shapefiles online the best I could find was and it looks really horrible, the same area in ggplot looks like . I ...
2
votes
1answer
232 views

Splitting strings into new rows, retaining geometry

UPDATED BELOW I have 9 shapefiles, each shapefile has 700,000+ rows and I have roughly 12 attribute fields in each shapefile. There are three attribute fields, common to every shapefile, that I am ...
2
votes
1answer
258 views

Convert multiple Shapefiles in Raster in R(and then plot it)

I'm trying to convert several shapefiles in rasters at the same time. I already was able to read the shapefiles by doing this: library(maptools) shps <- dir(getwd(), "*.shp") for (shp in shps) ...
2
votes
2answers
225 views

MODIS Level 1B batch process

I am a new MODIS Level 1B user. I have been using the MODIS Swath tool to process my images. However, I have over 1000 images to process. I was wondering if there a script available in IDL or R (very ...