Interpreting LogLikelihood For LDA Topic Modeling

svtorykh
svtorykh New Altair Community Member
edited November 2024 in Community Q&A

Hi RM Community,

 

Based on the attached picture, how should I interpret Loglikelihood values changing with number of topics. Is higher better or lower better. Does it needs to be squared to be positive?

 

Thanks!

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  • MartinLiebig
    MartinLiebig
    Altair Employee

    Hi,

    it's the negative LLH. The lower the better.

     

    BR,
    Martin

  • svtorykh
    svtorykh New Altair Community Member

    Thanks for prompt reply, so in this case -230000 is better than -240000 or vice versa?

  • MartinLiebig
    MartinLiebig
    Altair Employee
    Answer ✓

    Hi @svtorykh,

     

    -240000 is better.

     

    BR,

    Martin

  • svtorykh
    svtorykh New Altair Community Member

    Thanks so much Martin!

  • MartinLiebig
    MartinLiebig
    Altair Employee

    By the way, @svtorykh,

    one of the next updates will have more performance measures for LDA. Just need to find time to implement it. LLH by itself is always tricky, because it naturally falls down for more topics.

     

    BR,

    Martin

  • svtorykh
    svtorykh New Altair Community Member

    That would be very nice to have! Please keep us posted Martin!

  • jozeftomas_2020
    jozeftomas_2020 New Altair Community Member


    Hello. I want to find the optimal K-number for KMEANS with the LDA Loglikelihood value

    For me, using alpha and beta as heuristics for the top 5 is the highest. Now, how to use K optimally. Does anyone know how to help? Thanks a lot I searched a lot, but I did not find anything    :smileysad:

  • MartinLiebig
    MartinLiebig
    Altair Employee

    Hey @jozeftomas_2020,

    i am fairly confused. KMeans and LDA are fairly different models. Why and how do you want to mix them?

     

    ~Martin

  • jozeftomas_2020
    jozeftomas_2020 New Altair Community Member

    In the articles I have seen using the LDA to find optimal k, but I do not know how?
    And how can I understand which LDA has a better result? Alpha and beta need to be adjusted a little or too high to get a better result?

    I'm so sorry
    Thanks a lot

  • MartinLiebig
    MartinLiebig
    Altair Employee

    @svtorykh,

    i've added Perplexity as the default to the performance of LDA. Perplexity is defined as

    exp(-LLH/tokens)

    and should be minimized. That's somewhat what you see in common blog posts on LDA.

     

    It's not yet on the marketplace. Let's see when we have enough features to publish.

     

    Cheers,

    Martin

  • svtorykh
    svtorykh New Altair Community Member

    Thanks much!

  • MartinLiebig
    MartinLiebig
    Altair Employee

    Always happy to help! Will it be possible that you present your use case at RM Wisdom in October?

  • ayaRizk
    ayaRizk New Altair Community Member
    @svtorykh
    May I ask how you generated the evaluation plot? Is there a specific operator for that or plotted it outside of RapidMiner?

    Thanks!
    /Aya
  • MartinLiebig
    MartinLiebig
    Altair Employee
    Hi Aya,

    Optimize Parameters (Grid) can create the log for it.

    Best,
    Martin
  • ayaRizk
    ayaRizk New Altair Community Member
    Hi @mschmitz
    Yes, this works well. Thanks a lot!
    /Aya

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