[R] Graduated Symbol and Color Scale Coding Question

[Josh B]

I am mapping radio telemetry detections of shorebirds using ggmap. I want
the map to depict a specific point (lat/lon) where the bird was detected. I
want this depicted date of detection to be represented by a color scale.
However, multiple birds are detected at the same telemetry tower (lat/lon)
but at different dates. To avoid masking detections due to multiple birds
being detected at the same point at different dates I would like to include
a graduated point that will change size based upon the number of
individuals detected. The goal is to show what date a bird was detected at
a telemetry tower and how many birds were detected at that telemetry, using
a color scale and graduated symbol.

My thought is to have the graduated color symbol stack on itself... larger
symbol on the bottom and the smallest on the top.

p<-ggmap(gmap)
p+geom_point(data=df.tmp,aes(recvLon,recvLat,color=as.Date(ts),size=2)+scale_fill_gradient2(low="yellow",mid="orange",high="red")

I expected the map to portray the color gradient I called, but the color
scale is a range of blue (dark to light)? I get no errors and the map shows
a color scale of the time stamp like I want, but not the actual colors I
want.

Also, I do not know how to combine a graduated symbol with the color scale?

*Joshua N. Barth*

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