## Learn about stock Exchange

Two areas of analytical understanding are useful for trading

1. Very first those pointed out earlier in the day: some analytical methods focused on working on real time datasets. It indicates you know you are watching only an example of information and also you desire to extrapolate. You thus experience in test and out-of sample problems, overfitting and so forth... From this perspective, data-mining is much more focused on dead datasets (ie you can view just about all the information, you have got an in sample just problem) than statistical learning.

Because analytical learning is approximately working on real time dataset, the used maths that deal with all of them must give attention to a *two scales problem*:

$$\left\{\begin{array}{lcl} X_{n+1} &=& F_\theta(X_n, \xi_{n+1})\\ {\hat\theta}_{n+1} &=& L(\pi(X_n), {\hat\theta}_n) \end{array}\right.$$ in which $X$ may be the (multidimentional) state room to review (you have inside it your explanatory factors and the ones to predict), $F$ contains the characteristics of $X$ which need some variables $\theta$. The randomness of $X$ originates from the development $\xi$, which is i.i.d.

The purpose of statistical understanding would be to build a methodology $L$ ith as inputs a limited observation $\pi$ of $X$ and increasingly adjust an estimate $\hat\theta$ of $\theta$, in order that we shall know all that's required on $X$.

If you believe about using statistical understanding how to find the variables of a linear regression, we could model their state room similar to this: $$\underbrace{\left( \begin{array}{c} y_{n+1}\\ x_{n+1} \end{array}\right)}_{X_{n+1}} = \left[ \begin{array}{ccc} a & b & 1\\ 1 & 0 & 0\\ \end{array}\right] \cdot \underbrace{\left( \begin{array}{c} x_{n}\\1\\ \epsilon_{n+1} \end{array}\right)}_{\xi_{n+1}}$$ which hence allows to observe $(y, x)_n$ at any $n$; right here $\theta=(a, b)$.

Then you need discover a method to increasingly develop an estimator of $\theta$ utilizing our findings. Have you thought to a gradient descent regarding the L2 length between $y$ in addition to regression: $$C(\hat a, \hat b)_n = \sum_{k\leq n} (y_k - (\hat a \, x_k + \hat b))^2$$

Therefore we can build these characteristics: $${\hat a}_{n+1} = {\hat a}_n - \gamma_{n+1} \, \frac{\partial\, C({\hat a}_n, {\hat b}_n)_{n+1}}{\partial\, {\hat a}_n}$$ and similarly for $\hat b$.

Right here $\gamma$ is a weighting system.

Generally an excellent method to build an estimator should write correctly the criteria to attenuate and implement a gradient lineage that create the learning scheme $L$.

Going back to our initial general issue: we need some applied maths understand when couple dynamical methods in $(X, \hat\theta)$ converge, so we need to know developing estimating systems $L$ that converge towards original $\theta$.

To provide you with tips on these types of mathematical outcomes:

Today we could go back to the 2nd part of analytical learning that's very interesting for quant traders/strategists:

2. The outcome familiar with show the performance of analytical understanding techniques can be used to prove the performance of trading algorithms. To see that it is enough to read again the coupled dynamical system that enables to write statistical understanding: $$\left\{\begin{array}{lcl} M_{n+1} &=& F_\rho(M_n, \xi_{n+1})\\ {\hat\rho}_{n+1} &=& L(\pi(M_n), {\hat\rho}_n) \end{array}\right.$$

Today $M$ tend to be marketplace factors, $\rho$ is underlying PnL, $L$ is a trading strategy. Only change *minimizing a criteria* by maximizing the PnL.

See including Optimal split of sales across liquidity swimming pools: a stochatic algorithm method by: Gilles Pagès, Sophie Laruelle, Charles-Albert Lehalle, within report, writers show which to use this process to optimally divide an order across different black swimming pools at the same time mastering the ability regarding the swimming pools to provide exchangeability and utilising the brings about trade.

The analytical learning resources enables you to build iterative trading methods (many of them are iterative) and **show their efficiency**.