where &j(f) denotes j-th column of the matrix A(f), the asterisk represents transposition and complex conjugate operation.
The normalization in PDC is different than in DTF; PDC shows a ratio between the outflow from channel j to channel i to all outflows from the source channel j. For comparison, we may rewrite the DTF definition (17) using a notation similar to (18):
Here hj(f) denotes i-th column of the matrix H(f).
Another measure of (partial) direct causal relations is proposed in (Korzeniewska et al. 2003). The direct DTF (dDTF) function is defined as a product of a modification of the DTF (Fj in (20), with the denominator independent of frequency) with partial coherence.
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