Boxplot 对含有NaN的数据是如何处理的

Boxplot 对含有NaN的数据是如何处理的,用什么代码可以找出图中显示的离群点

http://ww2.mathworks.cn/help/stats/boxplot.html

If x is a vector, then the grouping variables must contain one row for each element of x. If x is a matrix, then the grouping variables must contain one row for each column of x. Groups that contain a missing value (NaN), an empty character vector, or an empty string in a grouping variable are omitted, and are not counted in the number of groups considered by other parameters.