gridStatsLevel2AM(level2AM, func, res)

# specify the path to GEDI level2A data (zip file)
outdir = tempdir()
level2A_fp_zip <- system.file("extdata",
                  "GEDI02_A_2019108080338_O01964_T05337_02_001_01_sub.zip",
                  package="rGEDI")

# Unzipping GEDI level2A data
level2Apath <- unzip(level2A_fp_zip,exdir = outdir)

# Reading GEDI level2A data (h5 file)
level2a<-readLevel2A(level2Apath=level2Apath)

# Get GEDI derived Elevation and Height Metrics
level2AM<-getLevel2AM(level2a)
head(level2AM)

#' Define your own function
mySetOfMetrics = function(x)
{
metrics = list(
   min =min(x), # Min of z
   max = max(x), # Max of z
   mean = mean(x), # Mean of z
   sd = sd(x)# Sd of z
   )
   return(metrics)
}

#' Computing a serie of GEDI metrics
ZTstats<-gridStatsLevel2AM(level2AM = level2AM, func=mySetOfMetrics(elev_highestreturn), res=0.005)
plot(ZTstats)

#' Computing the maximum of RH100 only
maxRH100<-gridStatsLevel2AM(level2AM = level2AM, func=max(rh100), res=0.005)
plot(maxRH100)

#' Computing the mean of ZG only
ZGmean<-gridStatsLevel2AM(level2AM = level2AM, func=mean(elev_lowestmode), res=0.005)
plot(ZGmean)

close(level2a)