对于有缺测值的数据取平均

使用：

y=cmean(x,k,c)

x为包括有nan的数据，仪器观测中经常会出现

k为对x取第几维方向的平均

c的值可以控制缺测的条件，例如c取50，表示这一维方向上，如果有值的观测超过50个值才取平均，否则取nan；如果c取-5，表示缺测数在5以下时才做平均，否则返回nan-calculate the statistical mean of data but tick off nan

Usage

y=cmean(x,|k) or y=cmean(x,k,|c), k can be []

when　[m,n,...]=size(x)

　if k==1, [1,n,...]=size(y)　

　　　if not set k, then k=1, but if m==1, k=k+1,>>...

　if k==2, [m,1,...]=size(y)

　if k>2, [m,n,...,1(k demension),...]=size(y).

　 you can squeeze(y) by yourself to remove the dim(whose size(y,dim)==1)

c can control output bo be nan or mean, c =0 by default(namely, not work)

　if c>0, if valuable numbers(notnan) < c, then output nan instead of mean

　if c<0, if nan numbers >= c, then output nan instead of mean