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jacobeisenstein / gt-nlp-class

Course materials for Georgia Tech CS 4650 and 7650, "Natural Language"
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Possible missing subscript on Equation for CRFs #29

Closed lzfelix closed 6 years ago

lzfelix commented 6 years ago

Dear professor Eisenstein,

Thank you very much for making the book publicly available. I would like to point a possible typo on the equation on section 7.5.3.1:

Should not the s function be written s_m, indicating the transition between labels y_{m-1} and y_m on the i-th position of the underlying w sequence?

Thank you very much, Luiz C F Ribeiro

yuvalpinter commented 6 years ago

Hi Luiz, IIRC s is a global transition matrix, which is not dependent on position. Yuval

lzfelix commented 6 years ago

Hi Yuval,

You are right regarding the transition matrix being global, irrespective to elements position.

I actually forgot the complete definition of s_m(y_m, y_{m-1}) from an example on the book, where the function is defined as a sum of the score of the m-th element of the sequence having the label y and the transition between tags. This is defined formally on Equation 7.16.

What caught my attention is that s has always a subscript on this chapter, except on this equation.

jacobeisenstein commented 6 years ago

Luis, you are correct. sm is indexed by m because it describes the score for the tag transition y{m-1} -> y_m specifically on position m. I will make an update. Thanks! -Jacob

On Tue, Jun 19, 2018 at 6:17 AM, Luiz Felix notifications@github.com wrote:

Hi Yuval,

You are right regarding the transition matrix being global, irrespective to elements position.

I actually forgot the complete definition of s_m(ym, y{m-1}) from an example on the book, where the function is defined as a sum of the score of the m-th element of the sequence having the label y and the transition between tags. This is defined formally on Equation 7.16.

What caught my attention is that s has always a subscript on this chapter, except on this equation.

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