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Adding colour to polylines in Leaflet

8 messages · Dhiraj Khanna, Kent Johnson

Original
Kent Johnson
# 
What are you expecting to see? When I run your code I get a map with three
lines, one red, one orange and one yellow.

Kent
Dhiraj Khanna
# 
@Kent they are appearing as three separate lines. I am hoping to see them
joint with no gaps. The transition from row 4 to row 5 is where the speed
has changed from 2.1 knots to 3.4 knots. I am hoping to see another line
from row 4 to row 5 in red colour. Similarly for the other disjoint points.
Regards

Dhiraj Khanna
Mob:09873263331
On Sat, Sep 1, 2018 at 6:17 PM Kent Johnson <kent3737 at gmail.com> wrote:

            

      
      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Kent Johnson
    

    

      
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You have to include the points where the colors change in both polylines.
Here is one way:

x$lastColor = dplyr::lag(x$Color)
map <-  leaflet(x)
map <- addTiles(map)
for( Color in
levels(as.factor(x$Color))){
  map <- addPolylines(map,lng=~lon,lat=~lat,data=x[x$Color==Color |
x$lastColor==Color,], color=~Color) }
map

Kent

On Sat, Sep 1, 2018 at 8:56 AM, Dhiraj Khanna <dhirajkhanna at gmail.com>
wrote:

            

      
      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Dhiraj Khanna
    

    

      
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Thank you Kent, that worked like a charm!
Regards

Dhiraj Khanna
Mob:09873263331

        
On Sat, Sep 1, 2018 at 7:59 PM Kent Johnson <kent3737 at gmail.com> wrote:

        

            

      
      
      
    

        

  
  


  


      

    

    
21 days later

    

      
      

        


  

        

      Dhiraj Khanna
    

    

      
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@Kent Johnson <kent3737 at gmail.com> guess I jumped the gun!

Your code worked like a charm as long as the colours were all in order, ie,
none of them are repeating.
Like I mentioned, I am working with shipping data and the Color variable is
dependent on the ship?s speed. The code that you provided joins all the
line segments which have the same color.
So if red represents a speed less than 3 knots, then it will join all the
points irrespective of the timeline wherever the color is red.

What I am looking for is one continuous path where the same color might
repeat. Here?s a reproducible example:

library(leaflet)
x <- structure(list(lat = c(51.88783, 51.8878441, 51.887825, 51.88659,
 51.8866959, 51.8874931, 51.89359, 51.8941269, 51.8977051, 51.8994331,
 51.90773, 51.91324, 51.91604, 51.9216652, 51.93353, 51.9419365 ),
                     lon = c(4.28763342, 4.287635, 4.28765154,
4.29007339, 4.29562664,  4.29917, 4.30641174, 4.30561829, 4.29263353,
4.284498, 4.261132,  4.24711847, 4.241075, 4.23262, 4.21523666,
4.1927),
                     rateOfTurn = c(0L,  0L, 0L, 0L, 0L, 0L, 0L, 0L,
0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L),
                     sogKts = c(0, 0, 0, 2.1, 3.4, 4.6, 3.5, 3.8, 7.4,
7.9, 8.8,9.1, 9.2, 9.2, 0.3, 0.4),
                     cog = c(15, 15, 15, 122.2, 70.4,      70, 323.2,
315.3, 289.3, 290.9, 303.8, 303.7, 308.9, 324.5, 304.9, 301.4),
                     heading = c(163, 162, 163, 106, 71, 71, 303,
298, 289, 294, 303, 303, 310, 324, 304, 302),
                     timestamp =
c("2018-07-19T05:27:34","2018-07-19T05:39:35", "2018-07-19T05:45:34",
"2018-07-19T05:57:37",
                                   "2018-07-19T06:02:48",
"2018-07-19T06:04:49", "2018-07-19T06:12:51", "2018-07-19T06:13:32",
                                   "2018-07-19T06:19:08",
"2018-07-19T06:21:41",      "2018-07-19T06:28:42",
"2018-07-19T06:32:50",
                                   "2018-07-19T06:34:37",
"2018-07-19T06:37:41", "2018-07-19T06:43:49", "2018-07-19T06:50:09"),
                     Color = c("red", "red", "red", "red", "orange",
"orange","orange", "orange", "orange", "orange", "yellow", "yellow",
                               "yellow", "yellow", "red", "red")),
row.names = 32:47, class = "data.frame")

#Kent's code

x$lastColor = dplyr::lag(x$Color)
map <-  leaflet(x)
map <- addTiles(map)
for( Color in
     levels(as.factor(x$Color))){
  map <- addPolylines(map,lng=~lon,lat=~lat,data=x[x$Color==Color |
x$lastColor==Color,], color=~Color) }
map

As you can see, the last two observations are again in red color. But when
the map renders, it joins the last two observations with the first three.

I am not sure what to do here? Inserting a row of NAs would help? But I am
also using another javascript plugin (polylineDecorator) for adding arrows
to the direction of travel and that is intolerant to NAs.
Appreciate some help here.


Regards
Dhiraj Khanna
Mob:09873263331

        
On Sat, Sep 1, 2018 at 8:06 PM Dhiraj Khanna <dhirajkhanna at gmail.com> wrote:

        

            

      
      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Kent Johnson
    

    

      
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Your problem is not really a leaflet problem, it is about identifying runs
in your data. This should help: https://stackoverflow.com/q/43875716/80626

Kent

On Sat, Sep 22, 2018 at 12:22 PM Dhiraj Khanna <dhirajkhanna at gmail.com>
wrote:

            

      
      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Kent Johnson
    

    

      
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Another approach is to draw individual line segments instead of polylines.
Here is one way; maybe there is a more elegant way to construct the
segments but this works...

library(tidyverse)
library(sf)
x = x %>% mutate(lat2=lead(lat, default=tail(lat, 1)),
                 lon2=lead(lon, default=tail(lon, 1))) %>%
  mutate(segment = st_sfc(crs=4326,
              pmap(.,
                 function(lat, lon, lat2, lon2, ...)
                   st_linestring(matrix(c(lon, lat, lon2, lat2),
                                        byrow=TRUE, ncol=2)))))

leaflet(x$segment) %>%
  addTiles() %>%
  addPolylines(color=x$Color)

Kent

        
On Sat, Sep 22, 2018 at 2:00 PM Kent Johnson <kent3737 at gmail.com> wrote:

        

            

      
      
      
    

        

  
  


  


      

    

    
1 day later

    

      
      

        


  

        

      Dhiraj Khanna
    

    

      
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@Kent Johnson <kent3737 at gmail.com> thank you so much for this. It does take
a bit of time to compute, but works nonetheless. Thanks again, appreciate!
Regards

Dhiraj Khanna
Mob:09873263331

        
On Sun, Sep 23, 2018 at 7:12 PM Kent Johnson <kent3737 at gmail.com> wrote: