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- Timestamp:
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Dec 22, 2010, 9:26:53 AM (14 years ago)
- Author:
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Víctor de Buen Remiro
- Comment:
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--
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v18
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v19
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69 | 69 | In this case we have that scalar distribution is the logistic one. |
70 | 70 | |
| 71 | ''Scalar cumulant'': [[BR]] |
71 | 72 | [[LatexEquation( F\left(z\right) = \frac{1}{1+e^{-z}} )]] [[BR]] [[BR]] |
72 | 73 | |
| 74 | ''Scalar density'': [[BR]] |
73 | 75 | [[LatexEquation( f\left(z\right) = \frac{e^{-z}}{\left(1+e^{-z}\right)^2} )]] [[BR]] [[BR]] |
74 | 76 | |
| 77 | ''Scalar density derivative'': [[BR]] |
75 | 78 | [[LatexEquation( f'\left(z\right) = - f\left(z\right) F\left(z\right) {\left(1-e^{-z}\right)} )]] [[BR]] [[BR]] |
76 | 79 | |
| 80 | ''Logarithm of likelihood'': [[BR]] |
77 | 81 | [[LatexEquation( L\left(\beta\right)=\underset{i}{-\sum}w_{i}\left(\ln\left(1+e^{-x_{i}^{t}\beta}\right)+\left(1-y_{i}\right)x_{i}^{t}\beta\right) )]] |
78 | 82 | |
| 83 | ''Gradient'': [[BR]] |
79 | 84 | [[LatexEquation( \frac{\partial L\left(\beta\right)}{\partial\beta_{j}}=\underset{i}{\sum}w_{i}\left(\frac{e^{-x_{i}^{t}\beta}}{1+e^{-x_{i}^{t}\beta}}-\left(1-y_{i}\right)\right)x_{ij} )]] |
80 | 85 | |
81 | | [[LatexEquation( \frac{\partial L\left(\beta\right)}{\partial\beta_{i}\partial_{j}}=\underset{k}{\sum}w_{k}\frac{-e^{-x_{k}^{t}\beta}}{\left(1+e^{-x_{k}^{t}\beta}\right)^{2}}x_{ki}x_{kj}=-\underset{k}{\sum}x_{ki}x_{kj}w_{k}\pi_{i}\left(1-\pi_{i}\right) )]] |
| 86 | ''Hessian'': [[BR]] |
| 87 | [[LatexEquation( \frac{\partial L\left(\beta\right)}{\partial\beta_{i}\partial_{j}}=\underset{k}{\sum}w_{k}\frac{-e^{-x_{k}^{t}\beta}}{\left(1+e^{-x_{k}^{t}\beta}\right)^{2}}x_{ki}x_{kj}=-\underset{k}{\sum}x_{ki}x_{kj}w_{k}\pi_{k}\left(1-\pi_{k}\right) )]] |
82 | 88 | |
83 | 89 | From the standpoint of arithmetic discrete numerical calculation must take into account that[[BR]] |
… |
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100 | 106 | In this case we have that scalar distribution is the standard normal one. |
101 | 107 | |
| 108 | ''Scalar cumulant'': [[BR]] |
102 | 109 | [[LatexEquation( F\left(z\right) = \Phi\left(z\right) )]] [[BR]] [[BR]] |
103 | 110 | |
| 111 | ''Scalar density'': [[BR]] |
104 | 112 | [[LatexEquation( f\left(z\right) = \phi\left(z\right) )]] [[BR]] [[BR]] |
105 | 113 | |
| 114 | ''Scalar density derivative'': [[BR]] |
106 | 115 | [[LatexEquation( f'\left(z\right) = -z \phi\left(z\right) )]] [[BR]] [[BR]] |
107 | 116 | |
| 117 | ''Logarithm of likelihood'': [[BR]] |
108 | 118 | [[LatexEquation( L\left(\beta\right)=\underset{i}{\sum}w_{i}\left(y_{i}\ln\left(\Phi\left(x_{i}\beta\right)\right)+\left(1-y_{i}\right)\ln\left(\Phi\left(-x_{i}\beta\right)\right)\right) )]] |
109 | 119 | |
| 120 | ''Gradient'': [[BR]] |
110 | 121 | [[LatexEquation( \frac{\partial L\left(\beta\right)}{\partial\beta_{j}}=\underset{i}{\sum}w_{i}\left(y_{i}\frac{\phi\left(x_{i}\beta\right)}{\Phi\left(x_{i}\beta\right)}-\left(1-y_{i}\right)\frac{\phi\left(x_{i}\beta\right)}{\Phi\left(-x_{i}\beta\right)}\right)x_{ij} )]] |
111 | 122 | |
| 123 | ''Hessian'': [[BR]] |
112 | 124 | [[LatexEquation( \frac{\partial L\left(\beta\right)}{\partial\beta_{i}\partial_{j}}=-\underset{k}{\sum}w_{k}\phi\left(x_{k}\beta\right)\left(y_{k}\frac{z\Phi\left(x_{k}\beta\right)+\phi\left(x_{k}\beta\right)}{\Phi^{2}\left(x_{k}\beta\right)}+\left(1-y_{k}\right)\frac{-z \Phi\left(-x_{k}\beta\right)+\phi\left(x_{k}\beta\right)}{\Phi\left(-x_{k}\beta\right)^{2}}\right)x_{ik}x_{jk} )]] |
| 125 | |
113 | 126 | |
114 | 127 | To avoid numerical problems will use the following equality |