How to compute the cross correlation coefficient between two signals with different lengths

Hi, there is a question about cross correlation coefficient between two signals with different lengths,such as, X=[1.2 2.1 3.0 5.4],Y=[1 5 6 7 9 12 2 4 11].Can the cross correlation coefficient be computed?if can,how to? I have computed it by using the equation r=corrcoef([X,Y]),but why the result is always one? Best wishes! Thank you!