I have notice that Log-likelihood statistics calculated with BFSU PowerConc are zero when coll-freq and conc-freq are equal. This is not the usual way and probably not the right way to do it.
I have referred to some discussions and documentation concerning this issue. Check out this page: http://ucrel.lancs.ac.uk/llwizard.html . Notes 2 on this page says, "when summing we can just ignore cells where x = 0."
I am working on a paper about collocation association measures and have studied how Dunning calculated LLR in the paper where he proposed this method. It is the same thing, simply ignoring the steps of summing where log(0) returns errors. I have written a VBA function that produces exactly the same results as Dunning's LLR method.
I don't know in what programming language PowerConc is written. In my VBA code I broke apart a long formula and used error traps before every line (suppose x is an expression resulting in zero):
On Error Resume Next
temp = temp + x * Log(x)
On Error Resume Next
temp = temp + y * Log(y)
By the way, according to BNCWEB manual, "There is a small error in the way BNCweb implements the log-likelihood formula: In principle, the calculation should be strictly binary and the above formula therefore does not contain the variable 'window span'."
I don't know if LL method is handled the same way in PowerConc. Personally I don't think it is necessary to give up "span", but a little modification is needed.
I have referred to some discussions and documentation concerning this issue. Check out this page: http://ucrel.lancs.ac.uk/llwizard.html . Notes 2 on this page says, "when summing we can just ignore cells where x = 0."
I am working on a paper about collocation association measures and have studied how Dunning calculated LLR in the paper where he proposed this method. It is the same thing, simply ignoring the steps of summing where log(0) returns errors. I have written a VBA function that produces exactly the same results as Dunning's LLR method.
I don't know in what programming language PowerConc is written. In my VBA code I broke apart a long formula and used error traps before every line (suppose x is an expression resulting in zero):
On Error Resume Next
temp = temp + x * Log(x)
On Error Resume Next
temp = temp + y * Log(y)
By the way, according to BNCWEB manual, "There is a small error in the way BNCweb implements the log-likelihood formula: In principle, the calculation should be strictly binary and the above formula therefore does not contain the variable 'window span'."
I don't know if LL method is handled the same way in PowerConc. Personally I don't think it is necessary to give up "span", but a little modification is needed.
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