wiki/scratch.page

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---
title: Scratch Page
toc: no
format: markdown
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# Math Stuff
On observation of $\mathcal{D}$, the *likelihood* of hypothesis
$\mathcal{R}_{\alpha}$ is
$\mathit{P}(\mathcal{D}|\mathcal{R}_{\alpha})$.
## Fingerprint Variance
Additionally, we associate a collective **RSS Variance**
$\sigma_{F_s}$ with each fingerprint, which is a weighed average of
the RSS values of each of the vector elements using $C_i$ as the
weight. It is calculated in this manner:
$$
\sigma_{F_s} = \frac{\sum_{i \in F_s} \sigma_i\, C_i}
{\sum_{i \in F_s} C_i}
$$
# Bayesian Regression
First, specify a set of probabilistic models of the data.
Let a member of this set be denoted by $\mathcal{R}_\alpha$
$\mathcal{R}_\alpha$ has a *prior* probability $P(\mathcal{H}_\alpha)$
On observation of $\mathcal{D}$, the *likelihood* of hypothesis
$\mathcal{R}_{\alpha}$ is
$\mathit{P}(\mathcal{D}|\mathcal{R}_{\alpha})$.
The *posterior* probability of $\mathcal{R}_{\alpha}$ is then given by
$\mathit{P}(\mathcal{H}_{\alpha})\mathit{P}(\mathcal{D}|\mathcal{H}_{\alpha})$
This follows from **Bayes' Theorem** which says
$$
P(A|B) = \frac{P(B | A)\, P(A)}{P(B)}
$$
# Matrix Stuff
This is a column vector:
$$\vec v = \left(\begin{matrix}
1\\
3\\
7
\end{matrix}\right)$$
The *vector sum* of $\vec u$ and $\vec v$ is:
$$\vec u + \vec v =
\left(\begin{matrix}
u_1\\
\vdots\\
u_n
\end{matrix}\right) + \left(\begin{matrix}
v_1\\
\vdots\\
v_n
\end{matrix}\right) = \left(\begin{matrix}
u_1 + v_1\\
\vdots\\
u_n + v_n
\end{matrix}\right)
$$
The *scalar multiplication* of the real number $r$ and the vector $\vec v$ is:
$$
r \cdot \vec v = r \cdot \left(\begin{matrix}
v_1\\ \vdots \\ v_n
\end{matrix}\right) = \left(\begin{matrix}
rv_1 \\ \vdots \\ rv_n
\end{matrix}\right)
$$