slightly modify correlation summation to compute absolute values
slightly modify correlation summation to compute absolute values

IntelPNI/fcma-toolbox,PrincetonUniversity/fcma-toolbox,IntelPNI/fcma-toolbox,EugeniaRadulescu/fcma-toolbox,jiminliang/fcma-toolbox,jiminliang/fcma-toolbox,IntelPNI/fcma-toolbox,EugeniaRadulescu/fcma-toolbox,PrincetonUniversity/fcma-toolbox,EugeniaRadulescu/fcma-toolbox,jiminliang/fcma-toolbox,PrincetonUniversity/fcma-toolbox