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添加955字节 、 2021年12月25日 (六) 19:09
无编辑摘要
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where [math]\displaystyle{ p_{Z\mid X}(\cdot\mid x;\theta ) }[/math] is the conditional distribution of the unobserved data given the observed data [math]\displaystyle{ x }[/math] and [math]\displaystyle{ D_{KL} }[/math] is the Kullback–Leibler divergence.
 
where [math]\displaystyle{ p_{Z\mid X}(\cdot\mid x;\theta ) }[/math] is the conditional distribution of the unobserved data given the observed data [math]\displaystyle{ x }[/math] and [math]\displaystyle{ D_{KL} }[/math] is the Kullback–Leibler divergence.
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<nowiki>其中 {\displaystyle p_{Z\mid X}(\cdot \mid x;\theta )}{\displaystyle p_{Z\mid X}(\cdot \mid x;\theta )} 是在给定观察数据{\displaystyle x}x前提下未观察到数据的条件分布, {\displaystyle D_{KL}}{\displaystyle D_{KL}} 是 Kullback–Leibler 散度。</nowiki>Then the steps in the EM algorithm may be viewed as:
Then the steps in the EM algorithm may be viewed as:
      
那么EM算法的步骤可以看成:
 
那么EM算法的步骤可以看成:
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Operate a Kalman filter or a minimum-variance smoother designed with current parameter estimates to obtain updated state estimates.
 
Operate a Kalman filter or a minimum-variance smoother designed with current parameter estimates to obtain updated state estimates.
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E步
    
操作一个 Kalman 滤波器或一个最小方差平滑设计与当前的参数估计,以获得更新的状态估计。
 
操作一个 Kalman 滤波器或一个最小方差平滑设计与当前的参数估计,以获得更新的状态估计。
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Use the filtered or smoothed state estimates within maximum-likelihood calculations to obtain updated parameter estimates.
 
Use the filtered or smoothed state estimates within maximum-likelihood calculations to obtain updated parameter estimates.
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M步
    
使用最大似然计算中的滤波或平滑状态估计来获得更新的参数估计。
 
使用最大似然计算中的滤波或平滑状态估计来获得更新的参数估计。
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where [math]\displaystyle{ \widehat{x}_k }[/math] are scalar output estimates calculated by a filter or a smoother from N scalar measurements [math]\displaystyle{ z_k }[/math]. The above update can also be applied to updating a Poisson measurement noise intensity. Similarly, for a first-order auto-regressive process, an updated process noise variance estimate can be calculated by
 
where [math]\displaystyle{ \widehat{x}_k }[/math] are scalar output estimates calculated by a filter or a smoother from N scalar measurements [math]\displaystyle{ z_k }[/math]. The above update can also be applied to updating a Poisson measurement noise intensity. Similarly, for a first-order auto-regressive process, an updated process noise variance estimate can be calculated by
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其中 < math > widehat { x } _ k <nowiki></math ></nowiki> 是由过滤器计算的标量输出估计值,或者由 n 个标量测量值计算得到的平滑器。上述更新也可以应用于泊松测量噪声强度的更新。同样,对于一阶自回归过程,更新后的过程噪声方差估计可以通过
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<nowiki>其中 {\displaystyle {\widehat {x}}_{k}}{\displaystyle {\widehat {x}}_{k}} 是由滤波器或平滑器从 N 个标量测量 {\displaystyle z_ {k}}z_{k}。 上述更新也可以应用于更新泊松测量噪声强度。 类似地,对于一阶自回归过程,更新的过程噪声方差估计可以计算为</nowiki>
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<nowiki>{\displaystyle {\widehat {\sigma }}_{w}^{2}={\frac {1}{N}}\sum _{k=1}^{N}{({\widehat {x} }_{k+1}-{\widehat {F}}{\widehat {x}}_{k})}^{2},}{\displaystyle {\widehat {\sigma }}_{w}^ {2}={\frac {1}{N}}\sum _{k=1}^{N}{({\widehat {x}}_{k+1}-{\widehat {F}}{ \widehat {x}}_{k})}^{2},}</nowiki>
    
where [math]\displaystyle{ \widehat{x}_k }[/math] and [math]\displaystyle{ \widehat{x}_{k+1} }[/math] are scalar state estimates calculated by a filter or a smoother. The updated model coefficient estimate is obtained via
 
where [math]\displaystyle{ \widehat{x}_k }[/math] and [math]\displaystyle{ \widehat{x}_{k+1} }[/math] are scalar state estimates calculated by a filter or a smoother. The updated model coefficient estimate is obtained via
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其中 < math > 和 < math > <nowiki></math ></nowiki> > > > > > > > x }{ k + 1} <nowiki></math ></nowiki> 是由过滤器或平滑器计算的标量状态估计。通过对模型参数的估计,得到了修正后的模型参数估计
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<nowiki>其中 {\displaystyle {\widehat {x}}_{k}}{\displaystyle {\widehat {x}}_{k}} {\displaystyle {\widehat {x}}_{k+1}}{ \displaystyle {\widehat {x}}_{k+1}} 是由过滤器或平滑器计算的标量状态估计。 更新后的模型系数估计是通过</nowiki>
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<nowiki>{\displaystyle {\widehat {F}}={\frac {\sum _{k=1}^{N}({\widehat {x}}_{k+1}-{\widehat {F}}{ \widehat {x}}_{k})}{\sum _{k=1}^{N}{\widehat {x}}_{k}^{2}}}.}{\displaystyle {\widehat {F}}={\frac {\sum _{k=1}^{N}({\widehat {x}}_{k+1}-{\widehat {F}}{\widehat {x}} _{k})}{\sum _{k=1}^{N}{\widehat {x}}_{k}^{2}}}</nowiki>
    
The convergence of parameter estimates such as those above are well studied.
 
The convergence of parameter estimates such as those above are well studied.
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