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| author | Jean Pouget-Abadie <jean.pougetabadie@gmail.com> | 2015-04-29 20:58:17 -0400 |
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| committer | Jean Pouget-Abadie <jean.pougetabadie@gmail.com> | 2015-04-29 20:58:17 -0400 |
| commit | 7fd038c7b0f00f6db411e9c5037133fd09509a8d (patch) | |
| tree | 61bbbae6b68049cd75ecf8596b48d1007bdcd8bc /paper/sections/results.tex | |
| parent | 42276753eeb857b3c085cead2c10315048c29a62 (diff) | |
| download | cascades-7fd038c7b0f00f6db411e9c5037133fd09509a8d.tar.gz | |
small reviewer updates
Diffstat (limited to 'paper/sections/results.tex')
| -rw-r--r-- | paper/sections/results.tex | 39 |
1 files changed, 23 insertions, 16 deletions
diff --git a/paper/sections/results.tex b/paper/sections/results.tex index f3c5366..b156897 100644 --- a/paper/sections/results.tex +++ b/paper/sections/results.tex @@ -20,7 +20,12 @@ a set $\mathcal{T}$ of observations. We will write $n\defeq |\mathcal{T}|$. \label{sec:main_theorem} In this section, we analyze the case where $\theta^*$ is exactly sparse. We -write $S\defeq\text{supp}(\theta^*)$ and $s=|S|$. Recall, that $\theta_i$ is the vector of weights for all edges \emph{directed at} the node we are solving for. In other words, $S$ is the set of all nodes susceptible to influence node $i$, also referred to as its parents. Our main theorem will rely on the now standard \emph{restricted eigenvalue condition}. +write $S\defeq\text{supp}(\theta^*)$ and $s=|S|$. Recall, that $\theta_i$ is the +vector of weights for all edges \emph{directed at} the node we are solving for. +In other words, $S$ is the set of all nodes susceptible to influence node $i$, +also referred to as its parents. Our main theorem will rely on the now standard +\emph{restricted eigenvalue condition}. +{\color{red} Add reference} \begin{definition} Let $\Sigma\in\mathcal{S}_m(\reals)$ be a real symmetric matrix and $S$ be @@ -29,7 +34,7 @@ write $S\defeq\text{supp}(\theta^*)$ and $s=|S|$. Recall, that $\theta_i$ is the 3\|X_S\|_1\}$. We say that $\Sigma$ satisfies the $(S,\gamma)$-\emph{restricted eigenvalue condition} iff: \begin{equation} - \forall X \in {\cal C(S)}, X^T \Sigma X \geq \gamma \|X\|_2^2 + \forall X \in {\cal C(S)}, X^T \Sigma X \geq \gamma \|X\|_2^2 \tag{RE} \label{eq:re} \end{equation} @@ -38,10 +43,12 @@ write $S\defeq\text{supp}(\theta^*)$ and $s=|S|$. Recall, that $\theta_i$ is the A discussion of the $(S,\gamma)$-{\bf(RE)} assumption in the context of generalized linear cascade models can be found in Section~\ref{sec:re}. In our setting we require that the (RE)-condition holds for the Hessian of the -log-likelihood function $\mathcal{L}$: it essentially captures the fact that the binary -vectors of the set of active nodes are not \emph{too} collinear. +log-likelihood function $\mathcal{L}$: it essentially captures the fact that the +binary vectors of the set of active nodes are not \emph{too} collinear. -We will also need the following assumption on the inverse link function $f$ of the generalized linear cascade model: +{\color{red} Rewrite the minimal assumptions necessary} +We will also need the following assumption on the inverse link function $f$ of +the generalized linear cascade model: \begin{equation} \tag{LF} \max\left(\left|\frac{f'}{f}(\inprod{\theta^*}{x})\right|, @@ -51,11 +58,11 @@ We will also need the following assumption on the inverse link function $f$ of t for some $\alpha\in(0, 1)$ and for all $x\in\reals^m$ such that $f(\inprod{\theta^*}{x})\notin\{0,1\}$. -In the voter model, $\frac{f'}{f}(z) = \frac{1}{z}$ and $\frac{f'}{f}(1-z) -= \frac{1}{1-z}$. Hence (LF) will hold as soon as $\alpha\leq \Theta_{i,j}\leq -1-\alpha$ for all $(i,j)\in E$ which is always satisfied for some $\alpha$ for non-isolated nodes. -In the Independent Cascade Model, $\frac{f'}{f}(z) -= \frac{1}{1-e^{-z}}$ and $\frac{f'}{1-f}(z) = -1$ and (LF) is not restrictive. +In the voter model, $\frac{f'}{f}(z) = \frac{1}{z}$ and $\frac{f'}{f}(1-z) = +\frac{1}{1-z}$. Hence (LF) will hold as soon as $\alpha\leq \Theta_{i,j}\leq +1-\alpha$ for all $(i,j)\in E$ which is always satisfied for some $\alpha$ for +non-isolated nodes. In the Independent Cascade Model, $\frac{f'}{f}(z) = +\frac{1}{1-e^{-z}}$ and $\frac{f'}{1-f}(z) = -1$ and (LF) is not restrictive. \begin{comment} Remember that in this case we have $\Theta_{i,j} = \log(1-p_{i,j})$. These @@ -189,12 +196,12 @@ solve the Graph Inference problem. Under the same assumptions as Theorem~\ref{thm:main}, let $\hat {\cal S}_\eta \defeq \{ j \in \{1,\ldots, m\} : \hat{\theta}_j > \eta\}$ for $\eta > 0$. For $\epsilon>0$ and $\epsilon < \eta$, let ${\cal S}^*_{\eta + \epsilon} \defeq \{ -i \in \{1,\ldots,m\} :\theta_i^* > \eta +\epsilon \}$ be the set of all true `strong' -parents. Suppose the number of measurements verifies: -$ n > \frac{9s\log m}{\alpha\gamma^2\epsilon^2}$. -Then with probability $1-\frac{1}{m}$, ${\cal S}^*_{\eta + \epsilon} \subseteq -\hat {\cal S}_\eta \subseteq {\cal S}^*$. In other words we recover all `strong' -parents and no `false' parents. +i \in \{1,\ldots,m\} :\theta_i^* > \eta +\epsilon \}$ be the set of all true +`strong' parents. Suppose the number of measurements verifies: $ n > +\frac{9s\log m}{\alpha\gamma^2\epsilon^2}$. Then with probability +$1-\frac{1}{m}$, ${\cal S}^*_{\eta + \epsilon} \subseteq \hat {\cal S}_\eta +\subseteq {\cal S}^*$. In other words we recover all `strong' parents and no +`false' parents. \end{corollary} \begin{proof} |
