(2.190”) 
Gi(w) Sy) 
Thus the multiple coherency v}(w) is 
OE Syx (@) f Syy(@) 
Sxx (@) Sxx (@) 
_ syx(@) syx(@) Tee 
= a ee yf = : 2.191 
AROGEO) SG) © OP 22» ee 
Here, as mentioned by L. Tick,?°H. Akaike,?” and Enochsen,”* the conditional 
spectum § 31@) is defined as 
2 
512(@) 
5,3 @) = 511@) - 522) X aC 
2 Isp(@)? _ Ilsio(@)I? 
Sy acon) 
= 511(@){1-y12(@)}. (2.192) 
This shows the spectrum of X;X; under the condition that X> has occurred, that is, the 
spectrum of XX; masked the effect of Xp. 
Generally, if the conditional spectrum of syx(w), under the condition that x; has 
occurred, is expressed by sya. ,(), then the partial coherency is defined as 
os (OS (2.193) 
Sire S19... LO Syy 2.3 x) 
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