You can simply plot a circular variable as a linear plot. For that, you don't need to do any transformation! For example -
You can plot the original data without telling R that it is a circular data.
Now you are telling R that it is a circular data class and these are the specifications. Like - these data points are basically angles, measured in radians and in clockwise direction.
windc <- circular(wind, type="angles",units="radians", zero = pi/2, rotation = "clock")
Now plot. It will generate a circular plot.
plot(windc, cex=1.5, bin=720, stack=TRUE, sep=0.030, shrink=1)
For more information see Circular statistics with R book.