sem

 SEM calculates the standard error of the mean
 
 [SE,M] = SEM(x [, DIM [,W]])
   calculates the standard error (SE) in dimension DIM
   the default DIM is the first non-single dimension
   M returns the mean. 
   Can deal with complex data, too. 

 DIM    dimension
    1: SEM of columns
    2: SEM of rows
     N: SEM of  N-th dimension 
    default or []: first DIMENSION, with more than 1 element
 W    weights to compute weighted mean and s.d. (default: [])
    if W=[], all weights are 1. 
    number of elements in W must match size(x,DIM) 

 features:
 - can deal with NaN's (missing values)
 - weighting of data 
 - dimension argument 
 - compatible to Matlab and Octave

 see also: SUMSKIPNAN, MEAN, VAR, STD