$lst_tit leveldata$lst_titend$type_both
$lst_alias levelpoints
$(lst_syntax)leveldata size $emph xsize,ysize$emphend
ranges $emph x1,x2,y1,y2$emphend function $emph f(x,y)$emphend
[levels $emph l1,l2,...$emphend]</tt>
$lst_mean ¼ÆËã $emph f(x,y)$emphend ÔÚˮƽ $emph l1,l2,...$emphend
(ĬÈÏÖµÊÇÒ»¸öˮƽ 0) ´¦µÄˮƽÇúÏßÉϵĵãµÄ×ø±ê. <p>
¼ÆË㷶Χ´Ó $emph (x1,y1)$emphend ÖÁ $emph (x2,y2)$emphend,
¼ÆËãͼÐÎÄÚ¹ØÓÚ $emph xsize,ysize$emphend µÄÕûÊýλÖõĵã. <p>
²ÎÊýÇø¶ÎµÄ´ÎÐò²»ÖØÒª, µ«³ýÁËˮƽÍâ¶¼ÊDZØÐëµÄ.