New design pattern chapter.
Next exercises for point processes.
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@@ -224,48 +224,3 @@
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\end{document}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section{\tr{Homogeneous Poisson process}{Homogener Poisson Prozess}}
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\begin{figure}[t]
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\includegraphics[width=1\textwidth]{poissonraster100hz}
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\caption{\label{hompoissonfig}Rasterplot von Poisson-Spikes.}
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\end{figure}
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The probability $p(t)\delta t$ of an event occuring at time $t$
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is independent of $t$ and independent of any previous event
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(independent of event history).
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The probability $P$ for an event occuring within a time bin of width $\Delta t$
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is
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\[ P=\lambda \cdot \Delta t \]
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for a Poisson process with rate $\lambda$.
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\subsection{Statistics of homogeneous Poisson process}
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\begin{figure}[t]
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\includegraphics[width=0.45\textwidth]{poissonisihexp20hz}\hfill
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\includegraphics[width=0.45\textwidth]{poissonisihexp100hz}
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\caption{\label{hompoissonisihfig}Interspike interval histograms of poisson spike train.}
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\end{figure}
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\begin{itemize}
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\item Exponential distribution of intervals $T$: $p(T) = \lambda e^{-\lambda T}$
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\item Mean interval $\mu_{ISI} = \frac{1}{\lambda}$
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\item Variance of intervals $\sigma_{ISI}^2 = \frac{1}{\lambda^2}$
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\item Coefficient of variation $CV_{ISI} = 1$
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\item Serial correlation $\rho_k =0$ for $k>0$ (renewal process!)
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\item Fano factor $F=1$
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\end{itemize}
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\subsection{Count statistics of Poisson process}
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\begin{figure}[t]
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\includegraphics[width=0.48\textwidth]{poissoncounthistdist100hz10ms}\hfill
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\includegraphics[width=0.48\textwidth]{poissoncounthistdist100hz100ms}
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\caption{\label{hompoissoncountfig}Count statistics of poisson spike train.}
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\end{figure}
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Poisson distribution:
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\[ P(k) = \frac{(\lambda W)^ke^{\lambda W}}{k!} \]
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@@ -113,3 +113,52 @@ Insbesondere ist die mittlere Rate der Ereignisse $r$ (``Spikes pro Zeit'', Feue
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% \end{figure}
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section{Homogener Poisson Prozess}
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F\"ur kontinuierliche Me{\ss}gr\"o{\ss}en ist die Normalverteilung
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u.a. wegem dem Zentralen Grenzwertsatz die Standardverteilung. Eine
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\"ahnliche Rolle spilet bei Punktprozessen der ``Poisson Prozess''.
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Beim homogenen Poisson Prozess treten Ereignisse mit einer festen Rate
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$\lambda=\text{const.}$ auf und sind unabh\"angig von der Zeit $t$ und
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unabh\"angig von den Zeitpunkten fr\"uherer Ereignisse. Die
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Wahrscheinlichkeit zu irgendeiner Zeit ein Ereigniss in einem kleinen
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Zeitfenster der Breite $\Delta t$ zu bekommen ist
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\[ P = \lambda \cdot \Delta t \; . \]
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\begin{figure}[t]
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\includegraphics[width=1\textwidth]{poissonraster100hz}
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\caption{\label{hompoissonfig}Rasterplot von Spikes eine homogenen
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Poisson Prozesse mit $\lambda=100$\,Hz.}
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\end{figure}
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Beim inhomogenen Poisson Prozess h\"angt die Rate $\lambda$ von der
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Zeit ab: $\lambda = \lambda(t)$.
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\begin{figure}[t]
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\includegraphics[width=0.45\textwidth]{poissonisihexp20hz}\hfill
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\includegraphics[width=0.45\textwidth]{poissonisihexp100hz}
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\caption{\label{hompoissonisihfig}Interspikeintervallverteilungen
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zweier Poissonprozesse.}
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\end{figure}
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Der homogne Poissonprozess hat folgende Eigenschaften:
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\begin{itemize}
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\item Die Intervalle $T$ sind exponentiell verteilt: $p(T) = \lambda e^{-\lambda T}$ .
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\item Das mittlere Intervall ist $\mu_{ISI} = \frac{1}{\lambda}$ .
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\item Die Varianz der Intervalle ist $\sigma_{ISI}^2 = \frac{1}{\lambda^2}$ .
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\item Der Variationskoeffizient ist also immer $CV_{ISI} = 1$ .
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\item Die seriellen Korrelationen $\rho_k =0$ for $k>0$, da das
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Auftreten der Ereignisse unabh\"angig von der Vorgeschichte ist. Ein
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solcher Prozess wird auch Erneuerungsprozess genannt (``renewal
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process'').
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\item Die Anzahl der Ereignisse $k$ innerhalb eines Fensters der L\"ange W ist Poissonverteilt:
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\[ P(k) = \frac{(\lambda W)^ke^{\lambda W}}{k!} \]
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\item Der Fano Faktor ist immer $F=1$ .
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\end{itemize}
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\begin{figure}[t]
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\includegraphics[width=0.48\textwidth]{poissoncounthistdist100hz10ms}\hfill
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\includegraphics[width=0.48\textwidth]{poissoncounthistdist100hz100ms}
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\caption{\label{hompoissoncountfig}Z\"ahlstatistik von Poisson Spikes.}
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\end{figure}
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