YGOLANA|ANALOGY

A blog about analogies found on the web.

Business is like Tree

From this post:
A business is like a tree. The roots of a “business tree” symbolize the strategic focus and future direction the organization is designed to grow. The trunk stands for the entire body of knowledge a business possesses. Branches stand for each department within a business. Twigs represent outside suppliers. And leaves on each branch symbolize employees.
With proper nourishment, the “business tree” will achieve healthy growth by growing steadily, optimally, and profitably. With neglect, the “business tree” will never reach its potential and eventually die.
 
And here is the book that covers the idea in depth:

MCMC is like Mountain

If you understand this description from Wikipedia, you don't need an analogy:
 
Markov Chain Monte Carlo (MCMC) methods (which include random walk Monte Carlo methods), are a class of algorithms for sampling from probability distributions based on constructing a Markov chain that has the desired distribution as its equilibrium distribution. The state of the chain after a large number of steps is then used as a sample from the desired distribution. The quality of the sample improves as a function of the number of steps.
 
If you don't have a clue what they are talking about, than this analogy may come handy. In fact this method is considered to be one of the top 10 most important algorithms ever.
 
So, here is the analogy:

Imagine that the posterior probability density of the model is a mountain, with higher probability parameters corresponding to points of higher elevation. Our goal is to summarize the topography of the mountain. Many of my colleagues are familiar with “hill-climbing algorithms”, wherein the algorithm looks for the mountain peak by taking the steepest path up from wherever it currently stands. (Familiar because they have using algorithms that do this, and often, since this is the pacific northwest, because they spend their weekends doing this themselves on actual mountains.)

MCMC is an approach that explores the mountain with a “drunken walk”, one carefully designed to stand at points of a given elevation for an amount of time proportional to the elevation.