R help - Dec 2016 - issue overlaying a contour plot on map

Hi R-community,
I am able to do a contour plot, and a map separately, but having some 
issues overlaying them. The script and data is attached.
test_filled_contour_plot.png is the contour plot alone
test_ggmap.png is the map alone.
test_overaly.png is supposed to overaly the two, but as you can see, 
it's not happening for some reason.
Any suggestions?
Cheers,
Jatin

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# Always delete everything first
rm(list = ls())
library(rgdal)
# load processed AERMOD outputs generated by read_AERMOD_save.R
load("ALL_HOURLY_NOX_Processed")
utmcoor<-SpatialPoints(cbind(x,y), proj4string=CRS("+proj=utm +zone=50
+ellps=WGS84 +south"))
longlatcoor<-spTransform(utmcoor,CRS("+proj=longlat"))
lon <-longlatcoor at coords[,1]
lat <-longlatcoor at coords[,2]
png("test_filled_countour_plot.png")
filled.contour(x=lon,y=lat,max_conc)
dev.off()
library(ggmap)
pngMAP_df = get_map(location = c(min(lon), min(lat), max(lon), max(lat)), source
= "osm", zoom = 12,filename="test_ggmap")
ggmap(pngMAP_df) + filled.contour(x=lon,y=lat,max_conc)
ggsave("test_overlay.png")
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Hi Jatin,
It looks as though the third plot has the contour plot beneath the
map, which is opaque.If you just want to show the three "hotspots" on
the map, perhaps you could adjust the colors so that they are
displayed on a transparent field instead of blue and then overlay that
on the map.

Jim


On Fri, Dec 9, 2016 at 7:02 PM, Jatin Kala <jatin.kala.jk at gmail.com>
wrote:
> Hi R-community,
> I am able to do a contour plot, and a map separately, but having some
issues
> overlaying them. The script and data is attached.
> test_filled_contour_plot.png is the contour plot alone
> test_ggmap.png is the map alone.
> test_overaly.png is supposed to overaly the two, but as you can see,
it's
> not happening for some reason.
> Any suggestions?
> Cheers,
> Jatin
>
>
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