MalletCRFStringOutcomeDataWriter and feature encoding

[Guy Dumais]

Hi all,

Any reason why MalletCRFStringOutcomeDataWriter does not write the Feature values?  I am referring to this piece of code in ClearTk's MalletCRFStringOutcomeDataWriter.

 @Override

68

  public void writeEncoded(List<NameNumber> features, String outcome) {

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    for (NameNumber nameNumber : features) {

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      this.trainingDataWriter.print(nameNumber.name);

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      this.trainingDataWriter.print(" ");

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    }

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    this.trainingDataWriter.print(outcome);

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    this.trainingDataWriter.println();

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  }

Note that this is not totally obvious from this piece of code but for Features of String type, the nameNumber.name field contains the encoded value with the name whereas for any other type (e.g. Boolean, Number, etc) the field nameNumber.name contains only the Feature name and not the value.

This seems like a bug to me, unless there is something that I miss.

Thanks in advance,

Guy Dumais 

[Steven Bethard]

I believe the issue is that the Mallet CRF format doesn't support anything other than strings:

http://mallet.cs.umass.edu/sequences.php

Please still file an issue though. If nothing else, MalletCRFStringOutcomeDataWriter should throw an exception to inform the user that non-String values aren't supported. An alternative would be to convert numbers into Strings and pass them on to Mallet, but I'm not confident that would do the sensible thing for, say, doubles.

Steve 

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[Guy Dumais]

I followed the approach you mentioned, that is, I convert integers to strings when creating a feature.  I will file an issue anyway.

Thanks for your help,

Guy.