Roger Bivand <[EMAIL PROTECTED]> wrote on 2007-04-09 13:52:45:
> On Mon, 9 Apr 2007 [EMAIL PROTECTED] wrote:
>
> > Roger's solution makes sense to me.
> >
> > The sinusoidal does have the appearance of pinching poleward, a
> > consequence of allocating equal area by spacing equally in both x
and y
Roger's solution makes sense to me.
The sinusoidal does have the appearance of pinching poleward, a
consequence of allocating equal area by spacing equally in both x and y.
Also the Lambert cylindrical sent in before should have had standard
parallels set to +/- 30, i.e.,
(See attached file: whem
For preview graphics and for large areas such as continents, large
countries, hemispheres, or the whole earth, spherical projections are
often adequate. I can provide some of the ones I have used. For
detailed work at sites and small areas, ellipsoidal projections such as
UTM are usually used, an
The thread below and many others in R-sig-Geo raise questions about
future directions. In reinventing GIS there are a whole list of
capabilities and functions that would be helpful. Some that I have
noticed include,
Topological representation to enable
Planar enforcement of boundary integr
Just found out a little about this in ArcGIS (ArcMap), version 9.1.
Yes, apparently with large datasets, the "natural breaks" classification
(and maybe others like quantile) does sample. However, it is possible
to change the sample size by clicking the "Sampling" button in the
Classification windo
[EMAIL PROTECTED] wrote on 2007-02-09 13:27:13:
> Andrew,
>
> Util the functionality is programmed in, here is a quick approximation
> to what you want:
>
> 1. generate a large number of random (or gridded) points within the
> polygon of interest in the first object (sample.polygon function in
> p
[EMAIL PROTECTED] wrote on 2007-01-26 00:34:22:
> On Fri, 26 Jan 2007, Pedro S. A. Wolf wrote:
>
> > I am a psychology student who has been using R to analyze
experimental data
> > mainly within the general linear model for about 2 years. I have
some
> > working knowledge with R, but by no means
Luis Ridao Cruz <[EMAIL PROTECTED]> wrote on 2006-11-29 03:40:25:
> R-sig-geo-help,
>
> I have locations of fish abundance
> which I want to aggregate into squares.
>
> The code below creates the grid:
>
>
> library(sp)
> test <- GridTopology(c(-10.5,60),c(0.1,0.1),c(67,35))
> coordinates(test)
>
Luis Ridao Cruz <[EMAIL PROTECTED]> wrote on 2006-11-29 03:40:25:
> R-sig-geo-help,
>
> I have locations of fish abundance
> which I want to aggregate into squares.
>
> The code below creates the grid:
>
>
> library(sp)
> test <- GridTopology(c(-10.5,60),c(0.1,0.1),c(67,35))
> coordinates(test)
>
Duncan Golicher <[EMAIL PROTECTED]> wrote on 2006-10-30 08:09:49:
> ...
>
> Also while posting, can anyone suggest a way of measuring the closest
> distance between disjunct polygons in R (forest fragments)? Its easy
to
> use centroids in spdep, but we were interested in the distances
between
> th
Roger Bivand <[EMAIL PROTECTED]> wrote on 2006-10-19 00:05:31:
> On Wed, 18 Oct 2006 [EMAIL PROTECTED] wrote:
>
> > I have a 1000 x 1000 grid of categorical values (nine of these) and
want
> > to compute and plot a correlogram. Function cell2nb() will take a
while
> > it appears but if that succe
-Roger Bivand <[EMAIL PROTECTED]> wrote: -On Wed, 18 Oct 2006 [EMAIL PROTECTED] wrote:> I have a 1000 x 1000 grid of categorical values (nine of these) and want> to compute and plot a correlogram. Function cell2nb() will take a while> it appears but if that succeeds then can methods of sp.
Yes, a "joincountogram" is the idea. Thanks for advice on size, I'll
try scaling up.
Roger Bivand <[EMAIL PROTECTED]> wrote on 2006-10-19 00:05:31:
> On Wed, 18 Oct 2006 [EMAIL PROTECTED] wrote:
>
> > I have a 1000 x 1000 grid of categorical values (nine of
> these) and want
> > to compute and
I have a 1000 x 1000 grid of categorical values (nine of these) and want
to compute and plot a correlogram. Function cell2nb() will take a while
it appears but if that succeeds then can methods of sp.correlogram() be
used on categorical data? What are "style" options in sp.correlogram()?
thanks,
Computing area on the spheroid:
Kimerling AJ. 1984. Area computation from geodetic coordinates on the
spheroid. Surveying and Mapping 44(4):343-351.
Measuring distortion:
Many cartography texts cover this. Analytical formulas for computing
distortion were developed by Tissot in the 19th century.
Has anyone implemented a t-test with the effective sample size
correction proposed by Dale and Fortin, Ecoscience 9(2):162-167, 2002,
using a discussion by Cressie, 1993, page 15?
thanks,
Denis
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[EMAIL PROTECTED] wrote: -
To: r-sig-geo@stat.math.ethz.ch
From: Colin Beale <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
Date: 31.01.2006 08:20
Subject: [R-sig-Geo] Grid projections and spatial matrices
Hi,
Two questions really (elaborated below): (1) Has anyone created what is
essentially
>I'm trying to plot some
>data for the Pacific Ocean and want to get a map onto my plot as
>well.
>I'm using the function 'map()' from library(maps). However, I cannot
>get it to plot anything across the dateline since it requires that
>longitudes between 180 and 360 degrees east to be written as
csr package:splancs R Documentation
Generate completely spatially random points on a polygon
Description:
Generate completely spatially random points on a polygon.
Usage:
csr(poly,npoints)
Arguments:
poly: A polygon data set.
npoints: The numbe
Here is a script using two functions. I hope this helps. Note that
this version of the stereographic projection uses a spherical model of
the earth not an ellipsoidal, and is set up for the north polar aspect
of the projection, since that appears to be most appropriate for the
kind of data you ha
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