用matlab编程绘制矩形窗函数的幅频特性，窗函数形状的长度为10，20，50，100.-Programming using matlab draw rectangle window function of the amplitude-frequency characteristics, the shape of window function of length of 10,20,50,100.

用ＭＡＴＬＡＢ实现不同线型、不同颜色，不同位置画出多个矩形-Using MATLAB to achieve different line, different colors, different locations to draw multiple rectangles