Re: [R-sig-Geo] centering map on Pacific Basin instead of Greenwich

[Chris Lusk]

Thanks Roger! After I transform all longitudes to positive values, your
solution works nicely.

Chris


*- - - - - - -*Chris Lusk
Environmental Research Institute
University of Waikato
Hamilton
New Zealand
Senior Editor, *New Zealand Journal of Botany*



On Wed, Nov 30, 2016 at 10:06 PM, Roger Bivand  wrote:

> On Wed, 30 Nov 2016, Chris Lusk wrote:
>
> Hello all
>>
>> I'm making a global map of average leaf size in forests, using different
>> colours to show dominance of different leaf size classes. The world map is
>> of course centred on Greenwich (longitude zero) but none of my data are
>> from Europe or Africa, so a map centred on the Pacific basin would look
>> much better. In fact I'd like to cut Europe and Africa right out of the
>> map
>> (nothing personal about this!).
>>
>> Online I've seen several suggestions for re-centering the map, but they
>> haven't worked for me. I would really appreciate suggestions about how to
>> achieve this.
>>
>
> mapdata comes with world2Hires, which is Pacific centred. However, the
> polygons are not split at 0, so wrap around if you need to fill. I think
> your xlim= values are incorrect too, I get a Pacific basin from:
>
> map("world2Hires", xlim=c(135, 290), ylim=c(-60,70), lty=1,
>  interior=FALSE)
>
> but as lines not filled polygons.
>
> Roger
>
>
>> My map code is pasted in below, and the data can be downloaded at
>> http://sci.waikato.ac.nz/sites/clusk/DivrepNZ.csv
>>
>> cheers
>>
>> Chris
>> 
>>
>> library(maps)
>> library(mapdata)
>> library(maptools)
>>
>> ###Get world map and fill landmasses to hide national borders
>> map("worldHires", xlim=c(-165,180),ylim=c(-60,70),lty=1, col="gainsboro",
>> fill=TRUE, border="gainsboro")
>>
>> ###Show axes with horizontal tick labels
>> map.axes(cex.axis=0.75, las=1)
>>
>> ###Make axis titles
>> title(xlab = "Longitude (degrees E)", ylab="Latitude (degrees S)")
>> ##Get site location data to plot
>>
>> Data = read.csv("DivrepNZ.csv")
>>
>> Mesophyll = subset (Data, Size == "Mesophyll", select = c("Size", "ID",
>> "lon", "lat"))
>> Notophyll = subset (Data, Size == "Notophyll", select = c("Size", "ID",
>> "lon", "lat"))
>> Microphyll = subset (Data, Size == "Microphyll", select = c("Size", "ID",
>> "lon", "lat"))
>> Nanophyll = subset (Data, Size == "Nanophyll", select = c("Size", "ID",
>> "lon", "lat"))
>>
>> points(Mesophyll[,"lon"], Mesophyll[,"lat"],pch=15, cex=0.6, col="red3")
>> points(Notophyll[,"lon"], Notophyll[,"lat"], pch=15, cex=0.6,
>> col="orange")
>> points(Microphyll[,"lon"], Microphyll[,"lat"], pch=15, cex=0.6,
>> col="green3")
>> points(Nanophyll[,"lon"], Nanophyll[,"lat"], pch=15, cex=0.6, col="blue")
>>
>>
>>
>>
>> *- - - - - - -*Chris Lusk
>> Environmental Research Institute
>> University of Waikato
>> Hamilton
>> New Zealand
>> Senior Editor, *New Zealand Journal of Botany*
>>
>> [[alternative HTML version deleted]]
>>
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>>
>>
> --
> Roger Bivand
> Department of Economics, Norwegian School of Economics,
> Helleveien 30, N-5045 Bergen, Norway.
> voice: +47 55 95 93 55; fax +47 55 95 91 00
> e-mail: roger.biv...@nhh.no
> http://orcid.org/-0003-2392-6140
> https://scholar.google.no/citations?user=AWeghB0J=en
> http://depsy.org/person/434412
>

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[R-sig-Geo] centering map on Pacific Basin instead of Greenwich

[Chris Lusk]

Hello all

I'm making a global map of average leaf size in forests, using different
colours to show dominance of different leaf size classes. The world map is
of course centred on Greenwich (longitude zero) but none of my data are
from Europe or Africa, so a map centred on the Pacific basin would look
much better. In fact I'd like to cut Europe and Africa right out of the map
(nothing personal about this!).

Online I've seen several suggestions for re-centering the map, but they
haven't worked for me. I would really appreciate suggestions about how to
achieve this.

My map code is pasted in below, and the data can be downloaded at
http://sci.waikato.ac.nz/sites/clusk/DivrepNZ.csv

cheers

Chris


library(maps)
library(mapdata)
library(maptools)

###Get world map and fill landmasses to hide national borders
map("worldHires", xlim=c(-165,180),ylim=c(-60,70),lty=1, col="gainsboro",
fill=TRUE, border="gainsboro")

###Show axes with horizontal tick labels
map.axes(cex.axis=0.75, las=1)

###Make axis titles
title(xlab = "Longitude (degrees E)", ylab="Latitude (degrees S)")
##Get site location data to plot

Data = read.csv("DivrepNZ.csv")

Mesophyll = subset (Data, Size == "Mesophyll", select = c("Size", "ID",
"lon", "lat"))
Notophyll = subset (Data, Size == "Notophyll", select = c("Size", "ID",
"lon", "lat"))
Microphyll = subset (Data, Size == "Microphyll", select = c("Size", "ID",
"lon", "lat"))
Nanophyll = subset (Data, Size == "Nanophyll", select = c("Size", "ID",
"lon", "lat"))

points(Mesophyll[,"lon"], Mesophyll[,"lat"],pch=15, cex=0.6, col="red3")
points(Notophyll[,"lon"], Notophyll[,"lat"], pch=15, cex=0.6, col="orange")
points(Microphyll[,"lon"], Microphyll[,"lat"], pch=15, cex=0.6,
col="green3")
points(Nanophyll[,"lon"], Nanophyll[,"lat"], pch=15, cex=0.6, col="blue")




*- - - - - - -*Chris Lusk
Environmental Research Institute
University of Waikato
Hamilton
New Zealand
Senior Editor, *New Zealand Journal of Botany*

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