Add a label to map at each leg start - r

Question

I'm plotting legs of a route to a ggmap. It works okay so far. I've been trying to add a label containing the order (n from the loop) of each leg.
I've tried +geom_text to the geom_leg() but I get the error :
Error in geom_leg(aes(x = startLon, y = startLat, xend = endLon, yend = endLat), :
non-numeric argument to binary operator
I'd appreciate any help adding a label to indicate the leg.
Data :
structure(c("53.193418", "53.1905138631287", "53.186744", "53.189836",
"53.1884117", "53.1902965", "53.1940384", "53.1934748", "53.1894004",
"53.1916771", "-2.881248", "-2.89043889005541", "-2.890165",
"-2.893896", "-2.88802", "-2.8919373", "-2.8972299", "-2.8814698",
"-2.8886692", "-2.8846099"), .Dim = c(10L, 2L))
Function :
create.map<-function(lst){
library("ggmap")
cncat<-c(paste(lst[,1],lst[,2],sep=","))
df2<-data.frame(cncat)
leg <-function(start, dest, order){
r<- route(from=start,to=dest,mode = c("walking"),structure = c("legs"))
c<- geom_leg(aes(x = startLon, y = startLat,xend = endLon, yend = endLat),
alpha = 2/4, size = 2, data = r,colour = 'blue')+
geom_text(aes(label = order), size = 3)
return (c)
}
a<-qmap('Chester, UK', zoom = 15, maptype = 'road')
for (n in 1:9){
l<-leg(as.character(df2[n,1]), as.character(df2[n+1,1]),n)
a<-a+l
}
a
}

Answer 1

Is this close? (Note: this calls your list of points way.points).
way.points <- as.data.frame(way.points,stringsAsFactors=FALSE)
library(ggmap)
rte.from <- apply(way.points[-nrow(way.points),],1,paste,collapse=",")
rte.to <- apply(way.points[-1,],1,paste,collapse=",")
rte <- do.call(rbind,
mapply(route, rte.from, rte.to, SIMPLIFY=FALSE,
MoreArgs=list(mode="walking",structure="legs")))
coords <- rbind(as.matrix(rte[,7:8]),as.matrix(rte[nrow(rte),9:10]))
coords <- as.data.frame(coords)
ggm <- qmap('Chester, UK', zoom = 15, maptype = 'road')
ggm +
geom_path(data=coords,aes(x=startLon,y=startLat),color="blue",size=2)+
geom_point(data=way.points,aes(x=as.numeric(V2),y=as.numeric(V1)),
size=10,color="yellow")+
geom_text(data=way.points,
aes(x=as.numeric(V2),y=as.numeric(V1), label=seq_along(V1)))
So this assembles a vector of from and to coordinates using apply(...), then uses mapply(...) to call route(...) with both vectors, returning the overall list of coordinates in a data frame rte. Because the coordinates are stored as, e.g. $startLat and $endLat, we form a coords data frame by adding the final $endLat and $endLong to rte to get the very last leg of the route. Then we use geom_path(...) to draw the path in one step. Finally we use geom_text(...) with x and y-values from the original way.points data frame, and we use geom_point(...) just to make them stand out a bit.

Answer 2

Here's a bare bones solution. I just added the labels to the finished ggmap object a. If you replace the line
a
with
lst2 <- data.frame(cbind(lst, leg = as.character(1:10) )
names(lst2) <- c("lat", "lon", "leg")
a <- a + geom_text(data=lst2,aes(x=lon,y=lat,label=leg),size=5, vjust = 0, hjust = -0.5)
return(a)
in your create.map function, you should get (roughly) the desired result. I might have reversed the lat and lon variables, and you probably want to tweak the size, location, etc. Hope this helps!