Developers Club geek daily blog

As we the analysis for retail did ABC, or "without half of liter will not understand"

3 years, 1 month ago
Proverbs in itself do not appear … Sometimes you get into such jungle of analytics that necessarily the hand with the hot reaches for locker (all right, we he knows is at each office).

But we will speak a little about other.

In retail, logistics, management of warehouse and stocks there is such thing as ABC analysis. About it many theoretical publications are already written. And, it seems, everything is rather simple and clear, but whether so it actually?

When the category manager or the marketing specialist of distribution network closely approaches carrying out ABC analysis at it inevitably there is the whole lots of questions, fluctuations and doubts. We will also work with them in this article!

Let's walk on algorithm of actions at ABC analysis in product distribution networks, exceptions to the rules which should be considered, we will set example of carrying out the analysis on commodity group of Alcoholic beverages (yes, those half of liter).

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The histogram and box with moustaches on fingers

3 years, 1 month ago
In this note I want to describe two types of diagrams for one-dimensional data, namely
  • histogram
  • box with moustaches


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Spectral method on the example of simple problems of matfizika

3 years, 1 month ago
In this article the pseudo-spectral method of numerical solution of the equations of matfizika used in computing hydrodynamics, geophysics, climatology and in many other areas is described.


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About the new 3D set - schools, the Kalashnikov, the Arctic greenhouse and other engineering projects of graduates of last courses

3 years, 1 month ago

We in KROK have very big center 3D - technologies for engineering application. Such technologies for responsible training in the immersion environment (how to service nuclear reactor, for example), evacuation working off (each of us can escape from any oil platform blindly) and other-other pieces, including the rule 34 are necessary.

Design solutions of Luzhniki stadium are shown on such scheme developed by our graduate. Engineers very much love such visual things at 40-50 indirectly interacting subsystems.

Immersion teaching tool for trainings of security polices of the subway

Now there is new set. The same — abrupt specialty, graduates is snatched away after the termination, many study at once "under position" from the large companies. Departure of last course — only 15 of 25 have reached examination. Training partially in English.

Training costs 12.000 dollars, but it is possible to arrive on "budget" — there are 25 free places at competition (part lower). Last year competition was 5 people with already available skills 3D into place.

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We prepare t-SNE

3 years, 1 month ago
Working on article "Deep learning on R...", I several times met mentioning of t-SNE — mysterious technology of nonlinear decrease in dimension and visualization of multidimensional variables (for example, here), have been intrigued and have decided to understand everything in parts. t-SNE is t-distributed stochastic neighbor embedding. The Russian option with "implementation of neighbors" to a certain extent sounds ridiculously therefore I will use further English acronym.

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We draw on tayla of the electronic card in MSSQL

3 years, 1 month ago
I want to tell readers of habra-community as using CLR Microsoft.SqlServer.Types library it is possible to create tayla for the electronic card. In article the speech about generation of the list of cartographic tayl for their further rendering will go. The algorithm of generation of tayl on the geometry of objects which is stored in the MS SQL 2008 database will be described. All process of rendering will be step by step considered on example at the end of article.


Basic data
Storage of tayl
Stages of preparation of tayl
The used functions
Example with the broken line
Intersection check
Tables for storage of images of tayl
Placement of icon on the tayl
Association of tayl
Drawing of geometry on the tayl

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Visualization of static and dynamic networks on R, part 4

3 years, 1 month ago
In the first part:
  • visualization of networks: what for? how?
  • visualization parameters
  • best practices — esthetics and productivity
  • data formats and preparation
  • the description of data sets which are used in examples
  • the beginning of work with igraph

In the second part: colors and fonts in diagrams R.

In the third part: parameters of graphs, tops and edges.

In this part: placements of network.

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Work with data of the average size in Python. Pandas and Seaborn

3 years, 1 month ago
When you work hard with data, it is necessary to build often diagrams and to do different conversions over tables. It is important to learn to do it quickly and minimum straining brain. The matter is that data analysis in many respects consists in inventing and check of hypotheses. It is more interesting to think out, of course, than to check. But it is necessary to do both. Good tools in the trained hands help to spend the minimum quantity of time and intellectual energy for technical work.

I have tried many tools: Excel, Python+Matplotlib, R+ggplot, Python+ggplot, has also stopped on linking of Python+Pandas+Seaborn. Has solved with their use already many problems and would like to share supervision.

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How to create interactive maps

3 years, 1 month ago

Recently the interactive map displaying demographic changes in Europe from 2001 to 2011 — the period to which the most detailed statistics from each municipality is available has been published. By means of color scale degree of decrease or increase in population literally in each point of Europe (except for Russia and the CIS countries) and Turkey is designated.

One of developers of the Airbnb team took part in work on creation of this demographic card. Want to learn how independently to create the similar project? Then welcome under kat.

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We generate PDF-files in the web project: wkhtmltopdf program

3 years, 1 month ago
During the work on the web project sometimes there is need to generate PDF-files with big tables: price lists on thousands of positions. There were different libraries for generation of the PDF-file from PHP-script:

• MPDF — based on the FPDF library allowing to generate PDF file from any html-code

and many different other libraries. The MPDF library, if not critical shortcoming in our case was the most powerful and suitable, besides, initially correctly working with Cyrillics: big tables and in general big files were extremely slowly generated. Moreover, often generation did not happen absolutely, and the script stopped with error 504.

Further search has helped to find the wkhtmltopdf program. Program site:

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