Sebastian:
I assume you were thinking of calculating distances of points recorded
with longitude and latitude? If that's the case, then it's an arc
distance of a Great Circle. This article on wikipedia summarizes what
the formula are, and you can code the formula in R very reasonably:
http://en.wikipedia.org/wiki/Great-circle_distance.
If the coordinates are projected, then regular Euclidean distance would
apply.
Hope this helps.
Cheers,
Dr. Danlin Yu
J. Sebastian Tello wrote:
Hi everybody,
Could anyone please point into a reference where I could find how to make
accurate calculations of distance between two points based on their geographic
coordinates? I need to write some R code that includes this transformation, but
i am not sure how to do it.
Thanks in advance for any help!
Sebastian
J. Sebastián Tello
Department of Biological Sciences
285 Life Sciences Building
Louisiana State University
Baton Rouge, LA, 70803
(225) 578-4284 (office and lab.)
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Today's Topics:
1. Changing colour gradient in Spatstat surface plot
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Message: 1
Date: Tue, 29 Apr 2008 16:27:59 +0800 (WST)
From: [EMAIL PROTECTED]
Subject: [R-sig-Geo] Changing colour gradient in Spatstat surface plot
To: r-sig-geo@stat.math.ethz.ch
Cc: [EMAIL PROTECTED], [EMAIL PROTECTED]
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain;charset=iso-8859-1
Graham Smith <[EMAIL PROTECTED]> writes:
I have produced a smoothed surface plot of
water depths (depths as marks) in spatstat, but the default colours
are oranges and reds. How do I change these to blues.
Can I redifne the colours in terrain.colors() or topo.colors(), or do
I need to use rainbow(). Or is its something different all together.
Yes, you can do all of these things. It is not true that the colours are
hard-wired.
I have tried the options I listed above , but can't get a syntax that
works, and haven't found the help any help at all (not for me anyway).
I presume that you are using smooth.ppp to smooth a marked point pattern,
yielding a pixel image (object of class "im") which you now want to
display in your chosen colours. So the relevant help file is
help(plot.im)
The help file explains that the argument 'col' determines the colours that
will be used. See the examples in the help file, or example(plot.im).
Here is an example of the whole process, starting from a marked point
pattern and finishing with a colour image:
library(spatstat)
data(longleaf)
Z <- smooth.ppp(longleaf)
plot(Z)
plot(Z, col=topo.colors(256))
Adrian Baddeley
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___________________________________________
Danlin Yu, Ph.D.
Assistant Professor
Department of Earth & Environmental Studies
Montclair State University
Montclair, NJ, 07043
Tel: 973-655-4313
Fax: 973-655-4072
email: [EMAIL PROTECTED]
webpage: csam.montclair.edu/~yu
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