说明：  怎么用matlab画带箭头的直线呢？看看这个程序，也许你能用得上，程序写了一段代码，代码在直线的一头画了箭头符号！
(How to use matlab draw a straight line with the arrow it? Look at this program, maybe you can apply, write a program code, the code of a straight line drawn on the arrow symbol!)