求出现次数最多的值，并返回真实值——求交集
a=[1,2,3,4,5,6,7,2,3,4,7,3]
h=histogram(a,min=min(a))
m=where(h ge 2,count)+min(a)  ;两种以上分类器结果相同则输出
print,h
IDL> print,m
          2           3           4           7

或

a=[1,2,3,4,5,6,7,2,3,4,4,3]
h=histogram(a,min=min(a),max=max(a))
big=max(h) ;输出次数最大值
m=where(h eq big,count)
print,h
print,m+min(a)

求出现次数最少的值，并返回真实值——求差集
a=[1,2,3,4,5,6,7,2,3,4,4]
h=histogram(a,min=min(a))
little=min(h)
m=where(h eq little,count)+min(a)
print,m

或

a=[1,2,3,4,5,6,7,2,3,4,4]
h=histogram(a,max=max(a),min=min(a))
little=min(h)
m=where(h eq little,count)+min(a)
print,m