BLAND_ALTMANN shows the Bland-Altman plot of two columns of measurements
   and computes several summary results. 

   bland_altman(m1, m2 [,group])
   bland_altman(data [, group])
   R = bland_altman(...)
 
   m1,m2 are two colums with the same number of elements
	containing the measurements. m1,m2 can be also combined 
       in a single two column data matrix. 
   group [optional] indicates which measurements belong to the same group
	This is useful to account for repeated measurements.  


 References:
 [1] JM Bland and DG Altman, Measuring agreement in method comparison studies. 
       Statistical Methods in Medical Research, 1999; 8; 135. 
       doi:10.1177/09622802990080204
 [2] P.S. Myles, Using the Bland– Altman method to measure agreement with repeated measures
	British Journal of Anaesthesia 99(3):309–11 (2007)
	doi:10.1093/bja/aem214

Package: nan