# shadenorm.R function
shadenorm = function(below=NULL, above=NULL, pcts = c(0.025,0.975), mu=0, sig=1, numpts = 500, color = "gray", dens = 40, 

                    justabove= FALSE, justbelow = FALSE, lines=FALSE,between=NULL,outside=NULL){

                      

    if(is.null(between)){

         below = ifelse(is.null(below), qnorm(pcts[1],mu,sig), below)

         above = ifelse(is.null(above), qnorm(pcts[2],mu,sig), above)

    }

    

    if(is.null(outside)==FALSE){

         below = min(outside)

         above = max(outside)

    }

    lowlim = mu - 4*sig

    uplim  = mu + 4*sig

            

    x.grid = seq(lowlim,uplim, length= numpts)

    dens.all = dnorm(x.grid,mean=mu, sd = sig)

    if(lines==FALSE){

          plot(x.grid, dens.all, type="l", xlab="X", ylab="Density")

    }

    if(lines==TRUE){

          lines(x.grid,dens.all)

    }

    

    if(justabove==FALSE){

        x.below    = x.grid[x.grid<below]

        dens.below = dens.all[x.grid<below]

        polygon(c(x.below,rev(x.below)),c(rep(0,length(x.below)),rev(dens.below)),col=color,density=dens) 

    }

    if(justbelow==FALSE){

        x.above    = x.grid[x.grid>above]

        dens.above = dens.all[x.grid>above]

        polygon(c(x.above,rev(x.above)),c(rep(0,length(x.above)),rev(dens.above)),col=color,density=dens)

    }

    

    if(is.null(between)==FALSE){

         from = min(between)

         to   = max(between)

         

         x.between    = x.grid[x.grid>from&x.grid<to]

         dens.between = dens.all[x.grid>from&x.grid<to]

         polygon(c(x.between,rev(x.between)),c(rep(0,length(x.between)),rev(dens.between)),col=color,density=dens)

    }

    

}