PDF of normalized gaussian random vector












1












$begingroup$


let $X$ be a Gaussian random vector in $R^n$ such that



$$X sim mathcal{N}(mathbf{0}, mathbf{I_n}),$$



How can I find the PDF of $frac{X}{|X|}$?










share|cite|improve this question









$endgroup$

















    1












    $begingroup$


    let $X$ be a Gaussian random vector in $R^n$ such that



    $$X sim mathcal{N}(mathbf{0}, mathbf{I_n}),$$



    How can I find the PDF of $frac{X}{|X|}$?










    share|cite|improve this question









    $endgroup$















      1












      1








      1


      2



      $begingroup$


      let $X$ be a Gaussian random vector in $R^n$ such that



      $$X sim mathcal{N}(mathbf{0}, mathbf{I_n}),$$



      How can I find the PDF of $frac{X}{|X|}$?










      share|cite|improve this question









      $endgroup$




      let $X$ be a Gaussian random vector in $R^n$ such that



      $$X sim mathcal{N}(mathbf{0}, mathbf{I_n}),$$



      How can I find the PDF of $frac{X}{|X|}$?







      probability probability-distributions






      share|cite|improve this question













      share|cite|improve this question











      share|cite|improve this question




      share|cite|improve this question










      asked Jan 10 at 3:26









      ShaoyuPeiShaoyuPei

      1828




      1828






















          1 Answer
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          active

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          1












          $begingroup$

          By rotation invariance / symmetry, the PDF is the uniform distribution on the unit sphere, so the PDF is the constant value $frac{1}{S_{n-1}}$
          where $S_{n-1} = frac{n pi^{n/2}}{Gamma(frac{n}{2}+1)}$ is the surface area of the unit sphere in $mathbb{R}^n$.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
            $endgroup$
            – ShaoyuPei
            Jan 11 at 1:22










          • $begingroup$
            What can be said when $Xsimmathcal{N}(mu,Sigma)$?
            $endgroup$
            – nullgeppetto
            Feb 20 at 19:43












          • $begingroup$
            @ShaoyuPei math.stackexchange.com/questions/3120506/…
            $endgroup$
            – angryavian
            Feb 21 at 20:34












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          1 Answer
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          1 Answer
          1






          active

          oldest

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          active

          oldest

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          active

          oldest

          votes









          1












          $begingroup$

          By rotation invariance / symmetry, the PDF is the uniform distribution on the unit sphere, so the PDF is the constant value $frac{1}{S_{n-1}}$
          where $S_{n-1} = frac{n pi^{n/2}}{Gamma(frac{n}{2}+1)}$ is the surface area of the unit sphere in $mathbb{R}^n$.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
            $endgroup$
            – ShaoyuPei
            Jan 11 at 1:22










          • $begingroup$
            What can be said when $Xsimmathcal{N}(mu,Sigma)$?
            $endgroup$
            – nullgeppetto
            Feb 20 at 19:43












          • $begingroup$
            @ShaoyuPei math.stackexchange.com/questions/3120506/…
            $endgroup$
            – angryavian
            Feb 21 at 20:34
















          1












          $begingroup$

          By rotation invariance / symmetry, the PDF is the uniform distribution on the unit sphere, so the PDF is the constant value $frac{1}{S_{n-1}}$
          where $S_{n-1} = frac{n pi^{n/2}}{Gamma(frac{n}{2}+1)}$ is the surface area of the unit sphere in $mathbb{R}^n$.






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
            $endgroup$
            – ShaoyuPei
            Jan 11 at 1:22










          • $begingroup$
            What can be said when $Xsimmathcal{N}(mu,Sigma)$?
            $endgroup$
            – nullgeppetto
            Feb 20 at 19:43












          • $begingroup$
            @ShaoyuPei math.stackexchange.com/questions/3120506/…
            $endgroup$
            – angryavian
            Feb 21 at 20:34














          1












          1








          1





          $begingroup$

          By rotation invariance / symmetry, the PDF is the uniform distribution on the unit sphere, so the PDF is the constant value $frac{1}{S_{n-1}}$
          where $S_{n-1} = frac{n pi^{n/2}}{Gamma(frac{n}{2}+1)}$ is the surface area of the unit sphere in $mathbb{R}^n$.






          share|cite|improve this answer











          $endgroup$



          By rotation invariance / symmetry, the PDF is the uniform distribution on the unit sphere, so the PDF is the constant value $frac{1}{S_{n-1}}$
          where $S_{n-1} = frac{n pi^{n/2}}{Gamma(frac{n}{2}+1)}$ is the surface area of the unit sphere in $mathbb{R}^n$.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Jan 10 at 4:18

























          answered Jan 10 at 4:12









          angryavianangryavian

          42.5k23481




          42.5k23481












          • $begingroup$
            sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
            $endgroup$
            – ShaoyuPei
            Jan 11 at 1:22










          • $begingroup$
            What can be said when $Xsimmathcal{N}(mu,Sigma)$?
            $endgroup$
            – nullgeppetto
            Feb 20 at 19:43












          • $begingroup$
            @ShaoyuPei math.stackexchange.com/questions/3120506/…
            $endgroup$
            – angryavian
            Feb 21 at 20:34


















          • $begingroup$
            sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
            $endgroup$
            – ShaoyuPei
            Jan 11 at 1:22










          • $begingroup$
            What can be said when $Xsimmathcal{N}(mu,Sigma)$?
            $endgroup$
            – nullgeppetto
            Feb 20 at 19:43












          • $begingroup$
            @ShaoyuPei math.stackexchange.com/questions/3120506/…
            $endgroup$
            – angryavian
            Feb 21 at 20:34
















          $begingroup$
          sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
          $endgroup$
          – ShaoyuPei
          Jan 11 at 1:22




          $begingroup$
          sorry , Indeed I know this result ,however I can't prove that .and I see some answer on this website but not quite get it .
          $endgroup$
          – ShaoyuPei
          Jan 11 at 1:22












          $begingroup$
          What can be said when $Xsimmathcal{N}(mu,Sigma)$?
          $endgroup$
          – nullgeppetto
          Feb 20 at 19:43






          $begingroup$
          What can be said when $Xsimmathcal{N}(mu,Sigma)$?
          $endgroup$
          – nullgeppetto
          Feb 20 at 19:43














          $begingroup$
          @ShaoyuPei math.stackexchange.com/questions/3120506/…
          $endgroup$
          – angryavian
          Feb 21 at 20:34




          $begingroup$
          @ShaoyuPei math.stackexchange.com/questions/3120506/…
          $endgroup$
          – angryavian
          Feb 21 at 20:34


















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