The plotting symbols used in Figure 11.1 were created in R. Write a function as described in Section 11.8.1 to create a set of PNG files that can be used as place marks on Google EarthTM. Rather than simply making circles, consider making other shapes, including a miniature plot of the data. Also, use a different color scheme than the yellow-orange-red palette.
This place mark function creates the icons by setting up a blank canvas that has a transparent background and no axes or labels. On this canvas draw a circle or some other shape and fill it with the desired color. The function should take as input a vector of colors and create a set of circles (or some other shape) as PNG files, one for each color. The png (), plot(), and draw circle () functions might be helpful. In addition, you might try making the symbols partially transparent so that when they overlap on the plot, they can still be seen.
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