TRIMEAN yields the weighted mean of the median and the quartiles
    m = TRIMEAN(y).

 The trimean is  m = (Q1+2*MED+Q3)/4
    with quartile Q1 and Q3 and median MED   

 N-dimensional data is supported
 
 REFERENCES:
 [1] http://mathworld.wolfram.com/Trimean.html

Package: nan