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rplotggplot2mapsggmap

Using R and ggplot to draw separate lines between GPS coordinates

I am struggling to plot some lines using ggplot in R. I need to connect each pairs (grouped by INDEX). The data I am using is:

INDEX | LATITUDE | LONGITUDE | VALUE
1       53,071118  -6,063786   40.3
1       53,076478  -6,067592   40.3
2       53,071118  -6,063786   60.7
2       53,099204  -6,067235   60.7

And the code:

require(ggmap);
require(ggplot2);
options(warn=-1)

mydata = read.delim2("mydata.csv", TRUE, "\t")
df=as.data.frame(mydata)

City="Dublin, Ireland"

baseMap = get_map(location = City, zoom = 11, maptype = "terrain")
map <- ggmap(baseMap) +
  geom_path(aes(x=LONGITUDE, y=LATITUDE, group=INDEX), data=df, alpha=0.2)
map

On the last two lines the error is "Error: Discrete value supplied to continuous scale". How can I overcome that?

Edit: I inserted

df$LATITUDE=as.numeric(as.character(df$LATITUDE))
df$LONGITUDE=as.numeric(as.character(df$LONGITUDE))
df$INDEX=as.numeric(as.character(df$INDEX))

and it started working. Bear in mind that the coordinates had to be with dots, not commas. the lines are connected to each other

Solution

  • I just needed adding 

    df$LATITUDE=as.numeric(as.character(df$LATITUDE))
df$LONGITUDE=as.numeric(as.character(df$LONGITUDE))
df$INDEX=as.numeric(as.character(df$INDEX))

    and replacing ',' in the data with '.'