Use ggplot2 in `plotFootprint`

[ronnyhdez]

Within the FREddyPro project we can run this to check the example plot:

> ## Load data
> data(fluxes)
> 
> ## Clean and de-spike the fluxes
> fluxes=cleanFluxes(fluxes,sdCor=TRUE,sdTimes=3,timesList=3,distCor=TRUE,
+                    thresholdList=list(H=c(-100,1000),LE=c(-100,1000)))
> 
> ## Use only non-NA data
> fluxes_noNA<-fluxes[which(!is.na(fluxes$L)),]
> 
> ## Displacement height
> d=17.42 ## Displacement height
> 
> ## Calculate input variables for the footprint model
> fluxes_noNA$z=(fluxes_noNA$X.z.d..L*fluxes_noNA$L)+d
> fluxes_noNA$zol=fluxes_noNA$z/fluxes_noNA$L
> 
> ## Calculate the footprint for day 853
> footprint=Calculate(fetch=500,height=33,grid=200,fluxes_noNA$wind_speed[853],
+                     fluxes_noNA$wind_dir[853],fluxes_noNA$u.[853],fluxes_noNA$zol[853],
+                     sqrt(fluxes_noNA$u_var[853]))
> 
> ## Plot the footprint
> plotFootprint(footprint)