[R-sig-Geo] making wrld_simpl longitude borders something other than (-180, 180)

[Nick Matzke]

Although, unfortunately, the exact code, but switching "moll" to "latlong",
produces screwups (horizontal lines throughout the plot). Any advice?

Works:
====================
pdffn = "wrld_simpl_moll.pdf"
pdf(file=pdffn, width=12, height=6)

data(wrld_simpl) #The world as a SpatialPolygonsDataFrame
#To avoid the lines crossing the map after reprojection we need to cut the
polygons at the new break:
w <- nowrapRecenter(wrld_simpl, offset = 180-90, avoidGEOS=TRUE)
#Then proceed with the reprojection (note the proj4 string for a mollweide
projection with 150°E as the new center)
wrld_reCentered <- spTransform(w, CRS("+proj=moll +lon_0=-90"))
plot(wrld_reCentered, border="grey", lwd=0.5)


dev.off()
cmdstr = paste0("open ", pdffn)
system(cmdstr)
====================


Produces screwups:
====================
pdffn = "wrld_simpl_latlong.pdf"
pdf(file=pdffn, width=12, height=6)

data(wrld_simpl) #The world as a SpatialPolygonsDataFrame
#To avoid the lines crossing the map after reprojection we need to cut the
polygons at the new break:
w <- nowrapRecenter(wrld_simpl, offset = 180-90, avoidGEOS=TRUE)
#Then proceed with the reprojection (note the proj4 string for a mollweide
projection with 150°E as the new center)
wrld_reCentered <- spTransform(w, CRS("+proj=longlat +lon_0=-90"))
plot(wrld_reCentered, border="grey", lwd=0.5)


dev.off()
cmdstr = paste0("open ", pdffn)
system(cmdstr)
====================

On Mon, Sep 14, 2015 at 4:04 PM, Nick Matzke <matzke at nimbios.org> wrote:

> Ah, this did it:
> http://stackoverflow.com/questions/17718928/how-to-switch-to-a-map-that-is-centered-on-the-china-instead-of-the-default-set
>
> (plotting to PDF helps speed it up)
>
> library(geosphere)
> library(gdata) # for read.xls
> library(maptools) # for e.g. wrld_simpl
> library(rgdal)
> library(gpclib)   # for polygon clipping
>
> pdffn = "wrld_simpl.pdf"
> pdf(file=pdffn, width=12, height=6)
>
> data(wrld_simpl) #The world as a SpatialPolygonsDataFrame
> #To avoid the lines crossing the map after reprojection we need to cut the
> polygons at the new break:
> w <- nowrapRecenter(wrld_simpl, offset = 180-100, avoidGEOS=TRUE)
> #Then proceed with the reprojection (note the proj4 string for a mollweide
> projection with 150°E as the new center)
> wrld_reCentered <- spTransform(w, CRS("+proj=moll +lon_0=-100"))
> plot(wrld_reCentered, border="grey", lwd=0.5)
>
>
> dev.off()
> cmdstr = paste0("open ", pdffn)
> system(cmdstr)
>
>
>
>
> On Mon, Sep 14, 2015 at 3:46 PM, Nick Matzke <matzke at nimbios.org> wrote:
>
>> Apologies, I got my wires crossed.
>>
>> What I meant was, how would I make a map where the left edge was at
>> longitude 100 (e.g. Thailand), and the right edge is at, say 99
>> (again Thailand).  The Pacific Ocean, and the International Dateline, would
>> be in the middle of this map.
>>
>> I tried the obvious thing:
>> plot(wrld_simpl, xlim = c(100, 99))
>>
>> ...but that produces a flipped map...
>>
>> Cheers!
>> Nick
>>
>>
>> On Mon, Sep 14, 2015 at 3:38 PM, Frede Aakmann Tøgersen <frtog at vestas.com
>> > wrote:
>>
>>> Hi Nick
>>>
>>> To be honest I do not understand your question so I am guessing that you
>>> probably only need to set the xlim to c(-100, 100). Here is an example:
>>>
>>> > data(wrld_simpl)
>>> > plot(wrld_simpl)
>>> > plot(wrld_simpl, xlim = c(-100, 100))
>>>
>>> Why would one wants to redefine the longitudes from the interval (-180,
>>> 180) to (-100, 100)?
>>>
>>>
>>> Yours sincerely / Med venlig hilsen
>>>
>>> Frede Aakmann Tøgersen
>>> Specialist, M.Sc., Ph.D.
>>> Plant Performance & Modeling
>>>
>>> Technology & Service Solutions
>>> T +45 9730 5135
>>> M +45 2547 6050
>>> frtog at vestas.com
>>> http://www.vestas.com
>>>
>>> Company reg. name: Vestas Wind Systems A/S
>>> This e-mail is subject to our e-mail disclaimer statement.
>>> Please refer to www.vestas.com/legal/notice
>>> If you have received this e-mail in error please contact the sender.
>>>
>>>
>>> -----Original Message-----
>>> From: R-sig-Geo [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of
>>> Nick Matzke
>>> Sent: 14. september 2015 06:51
>>> To: r-sig-geo at stat.math.ethz.ch
>>> Subject: [R-sig-Geo] making wrld_simpl longitude borders something other
>>> than (-180, 180)
>>>
>>> Hi all,
>>>
>>> I would like to plot wrld_simpl, but have the left and right edges of the
>>> map be at something like 100 degrees longitude, rather than (-180, 180).
>>>
>>> I tried messing with the bounding box with no luck.
>>>
>>> I can imagine something like burrowing into the object and subtracting 80
>>> degrees from all the longitudes, but I suspect there must be a better
>>> way?
>>>
>>> Any help appreciated!
>>> Nick
>>>
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>>>
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>>
>>
>

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