数据 x1 = [1 2 4], x2 = [5 2 3]
[y, ps] = mapminmax(x1) %归一化
y = –1.0000 -0.3333 1.0000
ps为结构体，内容是：
ps.name = ‘mapminmax’
ps.xrows = 1
ps.xmax = 4
ps.xmin = 1
ps.xrange = 3
ps.yrows = 1
ps.ymax = 1
ps.ymin = –1
ps.yrange = 2
转换规则：y = (ymax – ymin) * (x - xmin) / (xmax - xmin) + ymin
要对x2也应用同一种规则来规范化，即：
[y1, ps] = mapminmax(x1);
y2 = mapminmax(‘apply’, x2, ps)
反归一化：
xtt = mapminmax(‘reverse’, y1, ps);
-------参考文献：有关mapminmax的用法详解 by faruto