# What is the meaning of "marching in"?

I came across this sentence, and I'm not pretty sure of the exact meaning: "marching in the sample size..."

Can someone please explain what it means in the context of that sentence? Also, what would be a good synonym that produces the same idea/meaning of "marching in"?

Thanks

Hello Laundrette, the complete sentence is below:

"Then, the MCMC approach involves marching in the sample space based on acceptance criteria that consider the likelihood of the data given the parameters."

Hope this is clear.

Thanks for the thorough answer, Johan! Much appreciated!

Thanks for the thorough answer, Johan! Much appreciated!

### 3 Answers

- JohanLv 56 years agoFavorite Answer
This is more of a Math or Statistics question than really Words & Wordplay. MCMC is "Markov chain Monte Carlo", which is a group of iterative methods in statistics to numerically determine properties of a variable distribution based on a given dataset (= sample space). The algorithms of the method involve "walkers" that move around through the sample space, in order to incorporate the collected data into a better model at each iteration. Depending on the particular algorithm, the model and suitable starting parameters, the method can be fast or slow, and the "walker" can move through the sample space in small or large steps. If the steps are too large, the process wouldn't be stable and wouldn't lead to a solution. if the steps are too small, the process might eventually approach the answer but it will just take too long. The trick is to define suitable criteria to tell the "walkers" how and in which direction to move.

Of course a desirable feature of a good method would be that it's fast (in other words, a good approximation of the true distribution can be attained in as few iterations as possible), and in that case, the "walkers" could be figuratively described as "marching purposefully through the sample space".

So "marching in the sample space" just means "moving (or: taking steps) within the space of collected data, from one datapoint to another."

- Anonymous6 years ago
That is not a complete sentence. We would need to see the entire sentence in which that phrase occurred to be able to figure out what it means.

"Marching" has many different possible meanings. We need more context to figure out what it means in this case.

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You're most welcome, Drealist! And thank you for your appreciation!