The following Matlab project contains the source code and Matlab examples used for entropy, joint entropy and conditional entropy function for n variables.
H = entropy(S)
this command will evaluate the entropy of S, S should be row matrix
H = entropy([X;Y;Z])
this command will find the joint entropy for the 3 variables
H = entropy([X,Y],[Z,W])
this will find H(X,Y/Z,W).