pro autoscale,d,zmin,zmax

    n = n_elements(d)
    if n le 1000 then begin
        s = sort(d)
        zmin = d[s[n * 0.01]]
        zmax = d[s[n * 0.99]]
    endif else begin
        indx = randomu(seed,1000) * (n-1)
        v = d[indx]
        s = sort(v)
        zmin = v[s[ 10]]
        zmax = v[s[990]]
    endelse
end