RANKCORR calculated the rank correlation coefficient.
This function is replaced by CORRCOEF.
Significance test and confidence intervals can be obtained from CORRCOEF, too.

R = CORRCOEF(X, [Y, ] 'Rank');

The rank correlation   r = corrcoef(ranks(x)).
is often confused with Spearman's rank correlation.
Spearman's correlation is defined as
r(x,y) = 1-6*sum((ranks(x)-ranks(y)).^2)/(N*(N*N-1))
The results are different. Here, the former version is implemented.

see also: CORRCOEF, SPEARMAN, RANKS

REFERENCES:
[1] http://mathworld.wolfram.com/SpearmanRankCorrelationCoefficient.html
[2] http://mathworld.wolfram.com/CorrelationCoefficient.html