History: Extracted raster data from the static Google map png, loaded it on the R device through ggimage
.
library (png)
library (ggmap)
rasterArray <- readPNG ("My.png")
x = c (40.702147,40.718217,40.711614)
y = c (-74.012318,-74.015794,-73.998284)
myData <- data.frame (x, y)
print (ggimage (rasterArray, fullpage = TRUE, coord_equal = FALSE)
+ geom_point (aes (x = x, y = y), data = myData, colour = I("green"),
size = I(5), fill = NA))
I did run dput
on the rasterArray
but the output is of 20 MBs, can't post here.
BTW, this is the URL of that static map:
Question: For plotting "GPS coordinates" on the R device containing the map in pixels, do I need to scale
the data.frame
?
I saw this page: http://www-personal.umich.edu/~varel/rdatasets/Langren1644.html Do I need to do scaling the way they have shown here?
If yes, then what else other than the man page of scale
function do I need to understand to get this done?
Am I barking at the wrong tree?
I think your mistake was the following:
Here is how you should do it instead, in two steps:
get_map()
and save it to disk using save()
ggmap()
First, get the map.
library (ggmap)
# Read map from google maps and save data to file
mapImageData <- get_googlemap(
c(lon=-74.0087986666667, lat=40.7106593333333),
zoom=15
)
save(mapImageData, file="savedMap.rda")
Then, in a new session:
# Start a new session (well, clear the workspace, to be honest)
rm(list=ls())
# Load the saved file
load(file="savedMap.rda")
# Set up some data
myData <- data.frame(
lat = c (40.702147, 40.718217, 40.711614),
lon = c (-74.012318, -74.015794, -73.998284)
)
# Plot
ggmap(mapImageData) +
geom_point(aes(x=lon, y=lat), data=myData, colour="red", size=5)