Is the 'spherical' GaussianMixture Model of sklearn the same as performing k-means?












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The GaussianMixture() implementation in scikit-learn offers four different types of covariance matrices when fitting the model. One of those is the 'spherical' type, in which each component has its own single variance.



My question, isn't this the same as doing k-means on a dataset?










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    The GaussianMixture() implementation in scikit-learn offers four different types of covariance matrices when fitting the model. One of those is the 'spherical' type, in which each component has its own single variance.



    My question, isn't this the same as doing k-means on a dataset?










    share|improve this question

























      1












      1








      1








      The GaussianMixture() implementation in scikit-learn offers four different types of covariance matrices when fitting the model. One of those is the 'spherical' type, in which each component has its own single variance.



      My question, isn't this the same as doing k-means on a dataset?










      share|improve this question














      The GaussianMixture() implementation in scikit-learn offers four different types of covariance matrices when fitting the model. One of those is the 'spherical' type, in which each component has its own single variance.



      My question, isn't this the same as doing k-means on a dataset?







      python scikit-learn gaussian






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      asked Nov 26 '18 at 9:32









      ArchieArchie

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          K-Means is exactly like a Hard Assignment GMM, where each mixture component has isotropic variance, and they are all equal.



          Just being isotropic ('spherical') does not guarantee equivalence to K-Means. the variance should also be the same.

          More detailed explanation can be found here.






          share|improve this answer
























          • So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

            – Archie
            Nov 26 '18 at 12:47






          • 1





            Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

            – Dinari
            Nov 26 '18 at 12:51













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          1 Answer
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          active

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          1














          K-Means is exactly like a Hard Assignment GMM, where each mixture component has isotropic variance, and they are all equal.



          Just being isotropic ('spherical') does not guarantee equivalence to K-Means. the variance should also be the same.

          More detailed explanation can be found here.






          share|improve this answer
























          • So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

            – Archie
            Nov 26 '18 at 12:47






          • 1





            Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

            – Dinari
            Nov 26 '18 at 12:51


















          1














          K-Means is exactly like a Hard Assignment GMM, where each mixture component has isotropic variance, and they are all equal.



          Just being isotropic ('spherical') does not guarantee equivalence to K-Means. the variance should also be the same.

          More detailed explanation can be found here.






          share|improve this answer
























          • So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

            – Archie
            Nov 26 '18 at 12:47






          • 1





            Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

            – Dinari
            Nov 26 '18 at 12:51
















          1












          1








          1







          K-Means is exactly like a Hard Assignment GMM, where each mixture component has isotropic variance, and they are all equal.



          Just being isotropic ('spherical') does not guarantee equivalence to K-Means. the variance should also be the same.

          More detailed explanation can be found here.






          share|improve this answer













          K-Means is exactly like a Hard Assignment GMM, where each mixture component has isotropic variance, and they are all equal.



          Just being isotropic ('spherical') does not guarantee equivalence to K-Means. the variance should also be the same.

          More detailed explanation can be found here.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 26 '18 at 9:50









          DinariDinari

          1,694523




          1,694523













          • So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

            – Archie
            Nov 26 '18 at 12:47






          • 1





            Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

            – Dinari
            Nov 26 '18 at 12:51





















          • So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

            – Archie
            Nov 26 '18 at 12:47






          • 1





            Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

            – Dinari
            Nov 26 '18 at 12:51



















          So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

          – Archie
          Nov 26 '18 at 12:47





          So if the implementation would be that each component share the same single variance value, then the two are equivalent (combined with hard assignments)?

          – Archie
          Nov 26 '18 at 12:47




          1




          1





          Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

          – Dinari
          Nov 26 '18 at 12:51







          Yes, if the above conditions exist, then the likelihood some point x is a member of some gaussian, depends only on the distance from its mean, exactly like in K-Means, and during the re-evaluating of the Gaussians, you only evaluate its mean, by averaging all the points, which is too, exactly like in K-means (As you don't re-evaluate the variance).

          – Dinari
          Nov 26 '18 at 12:51






















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