i'm trying to use your suggested matlab code; mwwtest(x1,x2). But my 2010a matlab version doesn't recognize this code. How is this possible? or is it possible that mwwtest code was deleted since the result is equivalent to ranksum(x1,x2) code?

If that is the case, can i replace mwwtest with ranksum? What is the difference between Mann-whitney u test and wilcoxon ranksum test? My advisor is convinced that Mann-whitney tests the difference btw mean while ranksum tests difference of median or distribution rank.

My final question is if i change to perform ranksum code instead of your suggested mwwtest, ranksum doesn't support 1-tailed test. Is this true? How can I test 1-tailed of ranksum or mwwtest in matlab. I see there are possible way to test 1-tailed in ALGLIB (http://www.alglib.net/hypothesistesting/mannwhitneyu.php).