drvkde(x,drv,bandwidth,gridsize,range.x,binned=FALSE,se=TRUE)se=TRUE, it returns a list with fields
x.grid - grid points
est - kernel estimate of partial derivative of density function
indicated by drv
se - estimate of standard error of est. Otherwise if
se=FALSE, only x.grid and est are returned.
x.grid. If the binned counts are not supplied then they are computed
inside this function. This function doesn't need to be used directly as it called from
featureSignif.
featureSignif