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  1. PO
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    <p>Here's something I started last year and never got around to polishing properly but hopefully it should answer your question of joining points on a map with great circle lines, with the flexibility to customise lines, circles etc.</p> <p>I use the (my) rworldmap package for mapping, WDI for world bank data and geosphere for the great circle lines. The aim was to plot aid flows from all donor countries to all recipient countries (one plot per donor). Below is an example plot, and below that the code. Hope it helps. Would be nice to find time to pick it up again! Andy</p> <p><img src="https://i.stack.imgur.com/b5b9g.png" alt="Aid flow map using rworldmap, WDI &amp; geosphere packages"></p> <pre><code>library(rworldmap) library(WDI) # WORLD BANK INDICATORS ## lines of either type may obscure more than they add ##**choose line option here addLines &lt;- 'gc' #'none''straight' 'gc' if ( addLines == 'gc' ) library(geosphere) # setting background colours oceanCol = rgb(7,0,30,maxColorValue=255) landCol = oceanCol #produces a list of indicator IDs and names as a matrix indicatorList &lt;- WDIsearch('aid flows') #setting up a world map shaped plot window #*beware this is windows specific mapDevice('windows',width=10,height=4.5) year &lt;- 2000 #for(indNum in 1:2) for(indNum in 1:nrow(indicatorList)) { indID &lt;- indicatorList[indNum][1] donorISO3 &lt;- substr(indID,start=8,stop=10) dFdonor &lt;- WDI(indicator=indID,start=year,end=year) #divide by 10^6 for million dollars dFdonor[indID] &lt;- dFdonor[indID] * 1/10^6 sPDFdonor &lt;- joinCountryData2Map(dFdonor,nameJoinColumn='country',joinCode='NAME') #take out Antarctica sPDFdonor &lt;- sPDFdonor[-which(row.names(sPDFdonor)=='Antarctica'),] legendTitle=paste("aid flow from",donorISO3,year,"(millions US$)") mapBubbles(sPDFdonor, nameZSize=indID, plotZeroVals=FALSE, legendHoriz=TRUE, legendPos="bottom", fill=FALSE, legendTitle=legendTitle, oceanCol=oceanCol, landCol=landCol,borderCol=rgb(50,50,50,maxColorValue=255),lwd=0.5,lwdSymbols=1) #removed because not working , main=paste('donor', donorISO3,year) #now can I plot lines from the centroid of the donor to the centroids of the recipients xDonor &lt;- sPDFdonor$LON[ which(sPDFdonor$ISO3==donorISO3) ] yDonor &lt;- sPDFdonor$LAT[ which(sPDFdonor$ISO3==donorISO3) ] xRecips &lt;- sPDFdonor$LON[ which(sPDFdonor[[indID]] &gt; 0) ] yRecips &lt;- sPDFdonor$LAT[ which(sPDFdonor[[indID]] &gt; 0) ] amountRecips &lt;- sPDFdonor[[indID]][ which(sPDFdonor[[indID]] &gt; 0) ] ## straight lines if ( addLines == 'straight' ) { for(line in 1:length(xRecips)) { #col &lt;- 'blue' #i could modify the colour of the lines by the size of the donation #col=rgb(1,1,1,alpha=amountRecips[line]/max(amountRecips)) #moving up lower values col=rgb(1,1,0,alpha=sqrt(amountRecips[line])/sqrt(max(amountRecips))) lines(x=c(xDonor,xRecips[line]),y=c(yDonor,yRecips[line]),col=col, lty="dotted", lwd=0.5) #lty = "dashed", "dotted", "dotdash", "longdash", lwd some devices support &lt;1 } } ## great circle lines ## don't work well when donor not centred in the map ## also the loop fails at CEC &amp; TOT because not ISO3 codes if ( addLines == 'gc' &amp; donorISO3 != "CEC" &amp; donorISO3 != "TOT" ) { for(line in 1:length(xRecips)) { #gC &lt;- gcIntermediate(c(xDonor,yDonor),c(xRecips[line],yRecips[line]), n=50, breakAtDateLine=TRUE) #30/10/13 lines command failed with Error in xy.coords(x, y) : #'x' is a list, but does not have components 'x' and 'y' #adding sp=TRUE solved gC &lt;- gcIntermediate(c(xDonor,yDonor),c(xRecips[line],yRecips[line]), n=50, breakAtDateLine=TRUE, sp=TRUE) #i could modify the colour of the lines by the size of the donation #col=rgb(1,1,1,alpha=amountRecips[line]/max(amountRecips)) #moving up lower values col=rgb(1,1,0,alpha=sqrt(amountRecips[line])/sqrt(max(amountRecips))) lines(gC,col=col,lwd=0.5) } } #adding coasts in blue looks nice but may distract data(coastsCoarse) plot(coastsCoarse,add=TRUE,col='blue') #repeating mapBubbles with add=T to go on top of the lines mapBubbles(sPDFdonor, nameZSize=indID, plotZeroVals=FALSE, fill=FALSE, addLegend=FALSE, add=TRUE, ,lwd=2) #removed because not working : , main=paste('donor', donorISO3,year) #looking at adding country labels text(xRecips,yRecips,sPDFdonor$NAME[ which(sPDFdonor[[indID]] &gt; 0) ],col=rgb(1,1,1,alpha=0.3),cex=0.6,pos=4) #pos=4 right (1=b,2=l,3=ab) #add a title nameDonor &lt;- sPDFdonor$NAME[ which(sPDFdonor$ISO3==donorISO3) ] mtext(paste("Aid flow from",nameDonor,year), cex = 1.8, line=-0.8) #savePlot(paste("C:\\rProjects\\aidVisCompetition2012\\Rplots\\greatCircles\\wdiAidFlowLinesDonor",donorISO3,year,sep=''),type='png') #savePlot(paste("C:\\rProjects\\aidVisCompetition2012\\Rplots\\greatCircles\\wdiAidFlowLinesDonor",donorISO3,year,sep=''),type='pdf') } #end of indNum loop </code></pre>
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    1. COThis looks nice, good stuff. I'm not sure how to check but is the underlying map image vectorised? `geosphere` seems to not encourage zooming in/out. Also, since it looks like the package isn't maintained actively, I shall only upvote and not accept the answer. I hope the 15 points encourage you to take it up again :)
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    2. COThanks! Yes the `rworldmap` map is vector (an `sp` `SpatialPolygonsDataFrame`). You can tell this by saving the plot as a pdf (uncomment the penultimate line of the code and edit the path), then zoom in and you'll see lines not pixels.
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