Data pre-processing and feature engineering [closed] - feature-selection

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I have been doing some reading on data pre-processing and feature engineering including feature selection, feature importance and feature construction.
My understanding is that Feature engineer is applied in data preprocessing stage. Additionally, Feature importance is sometimes checked when applying machine learning models, some times ot is done internally in the modes.
My question:
Is feature engineering always implemented in pre-processing stage or sometimes could be performed in later stages?
Thank you
Shosho

Feature engineering is the process of creating new features using domain knowledge, where the term 'pre-processing is meant to data cleaning.
Here, answering your question there is no specific order for feature engineering process. it depends on the data and domain. you have to keep checking after creating new features and retrain the model with new features.
Normally performing feature engineering in early stages is preferred.

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I'm a second-year computer science student who has made it to the final stage of a placement interview. The interview process consists of a logical thinking test, a group activity, and an interview with the company's representatives.
I'm looking for tips on how to prepare for these three components of the interview and what I should expect from them. Specifically, I'm wondering:
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Why isn’t Mathematica not as popular as MATLAB or Python? [closed]

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Closed 4 years ago.
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I found it much better on visualisation but not many people using it. Why isn't mathematica not as popular as matlab or python?
MATLAB and Mathematica are different packages for different user groups. Both software tools have similar freeware versions including Octave (MATLAB), Maxima (Mathematica), and others.
MATLAB has realized its objectives as being a software package for prototyping, idea testing, and simulations. It is more popular with engineers and some scientists. This popularity is based, in part, on marketing to students and instructors, ease of use, and availability.
Mathematica is a difficult and yet powerful tool. It has a set of language options and the usage has been personally frustrating. I was excited about integration with R language, but I have found that integration to be lacking, so far. It is more popular with a few engineers, some scientists, and mathematicians. Mathematica's latest editions have desirable licensing for students and home users. While not free, expense is reasonable.
Both tools have limited use in some industries.
Licensing is much more expensive for industrial partners. Industry continues to tighten its belt. Therefore, if you plan to be in industry, it may be highly beneficial to experience the freeware options, which nowadays includes the packages mentioned above as well as R, Python, and others.

Where is the Open Source repository for Swift 2.0? [closed]

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Closed 7 years ago.
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Apple announced Swift becoming Open Source since now two weeks and in his web site https://developer.apple.com/swift, no information was provided to find repository, documentation or Linux implementation announced at WWDC.
Someone have information about this ?
If you have read it carefully it clearly says that it will be released later this year. So you will find no repository yet
Open Source Later this year Swift will be released as open source.
Swift’s unique combination of elegance, power, and safety has the
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www.swift.org

PLC Programming Best Practices [closed]

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Closed 8 years ago.
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I have recently inherited a PLC project. We are using Automation Direct PLCs and using the C-more software for writing ladder logic.
C-more allows me to add rungs for "Execute on every scan", "Execute when called", etc.
It also allows me to break out separate sections under each of these headings to attempt some organization.
Are there some agreed upon best practices for structuring ladder logic programs? I'm trying to bring some sanity to the development process.
Document as you go. Logic, elements, memory map, etc. Document for "the other person", even if that person is YOU. PLCs and their programs tend to have a LONG life, so you will be glad 1 year, 5 years or even 20 years down the road when you have to tweak/debug that PLC. You'll be glad you explained things in a little more detail by documenting it for "the other person".
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Hope this helps!

How can I learn about writing project specs? [closed]

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I recently read through Code Complete, and it recommends that I create a project specification before actually coding.
The book didn't go very far into detail about what 'specs' are, and how they are made. Because this is a crucial part of software development, I would like to know how to create quality specs that are not too exhaustive.
Where can I learn more about software specifications? Or any of the other prerequisites outlined in Code Complete?
Here's Joel's article on Function Design documents.
http://www.joelonsoftware.com/articles/fog0000000036.html
If you are looking for books, I can recommend two right now, and in fact, I ordered a third because it looked good.
The two I can recommend fully are:
Software Requirements (2nd Edition)
More about Software Requirements
I also ordered a third book:
Software Requirements Patterns
Joel Spolsky posted the functional spec to his CoPilot application along with a brief blog post about it.
http://www.joelonsoftware.com/articles/AardvarkSpec.html