急！！！如何改变坐标轴，让x坐标轴不顶头开始，如图

[cupsbug]

http://image.baidu.com/detail/index?picture_id=12339371779&from=0&user_id=326601447&album_id=401799274&column=&tag=%E9%BB%98%E8%AE%A4%E4%B8%93%E8%BE%91&pn=0&is_album=1#pn0&-1&id12339371779

[zwlfxh]

查一下axis

axis([xmin xmax ymin ymax])