[R-sig-Geo] Plot coordinates on world map with Robinson CRS - ggplot2

[Miluji Sb]

Thank you very much. This works perfectly. Appreciate it.

Sincerely,

Milu

On Mon, Feb 18, 2019 at 11:01 AM Michael Sumner <mdsumner using gmail.com> wrote:

> You are very close, just needed the expert-knowledge for the incantation
> required to transform the longlat points (as was already done for the
> prj.coord, btw).
>
> HTH: https://gist.github.com/mdsumner/afd9228aa1dc4652f8bf193cad4245aa
>
> It does come as a surprise to many that R's plotting is not unit or
> projection aware (well, it is sometimes, but not usually ... a modern
> example is ggplot2::geom_sf  and the sf package but you need quite a lot of
> prior-won expertise there too, good luck).
>
> Cheers, Mike.
>
> On Mon, 18 Feb 2019 at 20:01 Miluji Sb <milujisb using gmail.com> wrote:
>
>> Dear all,
>>
>> I am trying to plot coordinates on a world map with Robinson CRS. While
>> the
>> world map is generated without any issues, when I try to plot the points -
>> I only get a single point.
>>
>> The code I am using and the coordinates data is below. What am I doing
>> wrong? Any help/suggestions will be highly appreciated.
>>
>> library(data.table)
>> library(foreign)
>> library(readstata13)
>> library(rgdal)
>> library(maptools)
>> library(ggplot2)
>> library(dplyr)
>>
>> load(url("
>>
>> https://github.com/valentinitnelav/RandomScripts/blob/master/NaturalEarth.RData?raw=true
>> "))
>>
>> PROJ <- "+proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84
>> +units=m +no_defs"
>>
>> NE_countries_rob  <- spTransform(NE_countries, CRSobj = PROJ)
>> NE_graticules_rob <- spTransform(NE_graticules, CRSobj = PROJ)
>> NE_box_rob        <- spTransform(NE_box, CRSobj = PROJ)
>>
>> # project long-lat coordinates for graticule label data frames
>> # (two extra columns with projected XY are created)
>> prj.coord <- project(cbind(lbl.Y$lon, lbl.Y$lat), proj=PROJ)
>> lbl.Y.prj <- cbind(prj.coord, lbl.Y)
>> names(lbl.Y.prj)[1:2] <- c("X.prj","Y.prj")
>>
>> prj.coord <- project(cbind(lbl.X$lon, lbl.X$lat), proj=PROJ)
>> lbl.X.prj <- cbind(prj.coord, lbl.X)
>> names(lbl.X.prj)[1:2] <- c("X.prj","Y.prj")
>>
>> m <- ggplot() +
>>   # add Natural Earth countries projected to Robinson, give black border
>> and fill with gray
>>   geom_polygon(data=NE_countries_rob, aes(long,lat, group=group),
>> colour="black", fill="gray80", size = 0.25) +
>>   # Note: "Regions defined for each Polygons" warning has to do with
>> fortify transformation. Might get deprecated in future!
>>   # alternatively, use use map_data(NE_countries) to transform to data
>> frame and then use project() to change to desired projection.
>>   # add Natural Earth box projected to Robinson
>>   geom_polygon(data=NE_box_rob, aes(x=long, y=lat), colour="black",
>> fill="transparent", size = 0.25) +
>>   # add graticules projected to Robinson
>>   geom_path(data=NE_graticules_rob, aes(long, lat, group=group),
>> linetype="dotted", color="grey50", size = 0.25) +
>>   # add graticule labels - latitude and longitude
>>   geom_text(data = lbl.Y.prj, aes(x = X.prj, y = Y.prj, label = lbl),
>> color="grey50", size=2) +
>>   geom_text(data = lbl.X.prj, aes(x = X.prj, y = Y.prj, label = lbl),
>> color="grey50", size=2) +
>>   # the default, ratio = 1 in coord_fixed ensures that one unit on the
>> x-axis is the same length as one unit on the y-axis
>>   coord_fixed(ratio = 1) +
>>   geom_point(data=df,
>>              aes(x=lon, y=lat), colour="Deep Pink",
>>              fill="Pink",pch=21, size=2, alpha=I(0.7))
>>   # remove the background and default gridlines
>>   theme_void()
>>
>> ## coordinates dataframe
>> dput(df)
>> structure(list(lon = c(2.67569724621467, 17.5766416259819,
>> 28.4126232192772,
>> 23.8147674538232, 29.8917589327105), lat = c(28.1503115976162,
>> -12.3388787380201, 9.78891068739477, -22.1873831176644, -3.36546931479253
>> )), class = "data.frame", row.names = c(NA, -5L))
>>
>> Sincerely,
>>
>> Milu
>>
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>>
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> --
> Dr. Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> 203 Channel Highway
> Kingston Tasmania 7050 Australia
>
>

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