[R-sig-Geo] Adding great circle routes as polylines in Leaflet

[Dhiraj Khanna]

Ben and Kent, thank you so much for your replies. Both work!

@Ben next time will make sure the code is more “calorie-free” :)

@Kent Johnson <kent3737 using gmail.com> I modified the weight for the lines by
using a scaling factor.

myScale <- function(x){(x-min(x))/(max(x)-min(x))}

ByRoute$AvgTCE <- myScale(ByRoute$AvgTCE)*5 + 1

@Kent Johnson <kent3737 using gmail.com> yes, this is shipping data and you are
right, great circle routes are not the best visualization. The problem I am
facing is that I have oil trade happening over a period of time from
various ports that I need to visualize. Over the selected period of time,
there are hundreds of voyages being undertaken by ships. Plotting them all
as gc routes looks ugly. My approach has been to classify these ports into
regions, which I drew using mapedit and saved them as SF polygons. I then
calculated their centroids and those are the coordinates in the ByRoute
dataframe. Would appreciate your comments on any other visualization which
you think might be appropriate.

Regards
Dhiraj Khanna
Mob:09873263331

On Mon, Sep 3, 2018 at 10:22 PM Kent Johnson <kent3737 using gmail.com> wrote:

> From: Dhiraj Khanna <dhirajkhanna using gmail.com>
>> To: r-sig-geo using r-project.org
>> Subject: [R-sig-Geo] Adding great circle routes as polylines in
>>         Leaflet
>> Message-ID:
>>         <CANHhK31knXB+8ev2LEQWOa3y+ZaUgkJ5noAV=
>> iX7Z14j_foqZw using mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> I am trying to add great circle routes between various regions in R.
>>
>> I would like to plot great circle routes between CommencingRegion to
>> LoadingRegion and then from LoadingRegion to DischargeRegion for every
>> row.
>> Additionally, every row needs to be in a different color and the thickness
>> needs to be proportional to AvgTCE. The last 6 variables in the data above
>> are the coordinates in Lat Long for the commencing, loading and
>> discharging
>> regions respectively. I am quite clueless on how to go about achieving
>> this. This is what I have tried and failed:
>>
>> leaflet() %>%
>>   addTiles() %>%
>>   for(i in 1:6){
>>
>> addPolylines(data=gcIntermediate(c(ByRoute$CLon[i],ByRoute$CLat[i]),c(ByRoute$LLon[i],ByRoute$CLat[i]),n=100,addStartEnd
>> = T,sp=T))
>>   }
>>
>> Here is a (rather clunky) start:
> library(leaflet)
> library(geosphere)
> library(dplyr)
>
> d = byRoute %>%
>   rowwise() %>%
>   do(leg1=gcIntermediate(c(.$CLon, .$CLat), c(.$LLon, .$LLat), n=50,
> addStartEnd=TRUE),
>      leg2=gcIntermediate(c(.$LLon, .$LLat), c(.$DLon, .$DLat), n=50,
> addStartEnd=TRUE))
>
> colors=palette()
> map = leaflet() %>% addTiles()
> for (i in seq_len(nrow(d)))
>   map = map %>% addPolylines(data=d$leg1[[i]], color=colors[i],
> weight=byRoute$AvgTCE[i]/3000-5) %>%
>   addPolylines(data=d$leg2[[i]], color=colors[i],
> weight=byRoute$AvgTCE[i]/3000-5)
> map
>
> You will have to split the great circles using something like
> the plot_my_connection function here:
>
> https://www.r-graph-gallery.com/how-to-draw-connecting-routes-on-map-with-r-and-great-circles/
>
> Is this shipping data? Maybe great circles are not the correct route...
> Kent
>
>
>> Regards
>> Dhiraj Khanna
>> Mob:09873263331
>
>

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