Hi all, I have this file 
__DATA__
child,    Parent,    probability,
M7,    Q,    P,
M7,      M28,     E,
M28,     M6,      E,
M6,      Q,      Pl,
& several hundred lines.....

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Legends: P(= Probable) > Pl(=Plausible) > E(=Equivocal). What I want is for each child I want to trace it back to Q(Query), but I need the shortest path which leads it to the Q(Query) along with their probabilities. For example for the input data shown above the output should be :- 
__OUTPUT_1__
M7:  M7<-Q = P
M28: M28<-M6<-Q = Pl.E
M6:  M6<-Q = Pl

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But as we can see from second row of input data M7 has another longer path tracing to Q : M7<-M28<-M6<-Q = Pl.E.E. But the code should have an option to neglect the largest path and thus show only the shortest path OR to show all of them. i.e. 
__OUTPUT_2__
M7:  M7<-Q = P
M7:  M7<-M28<-M6<-Q = Pl.E.E
M28: M28<-M6<-Q = Pl.E
M6:  M6<-Q = Pl

[download]
Thus this second output prints a path tracing back to Q for each of the rows, so if we have N input rows to the program , we will have N corresponding output rows.

In reply to find shortest path for each query from a CSV file by zing

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