User talk:Ksaareme

Git

   The object database contains four types of objects:

   A blob (binary large object) is the content of a file. Blobs have no file name, time stamps, or other metadata.
   A tree object is the equivalent of a directory. It contains a list of file names, each with some type bits and the name of a blob 
   or tree object that is that file, symbolic link, or directory's contents. This object describes a snapshot of the source tree.
   A commit object links tree objects together into a history. It contains the name of a tree object (of the top-level source directory),
   a time stamp, a log message, and the names of zero or more parent commit objects.
   A tag object is a container that contains reference to another object and can hold additional meta-data related to another object. 
   Most commonly, it is used to store a digital signature of a commit object corresponding to a particular release of the data being tracked by Git.

   heads
   refers to an object locally.
   remotes
   refers to an object which exists in a remote repository.
   stash
   refers to an object not yet committed.
   meta
   e.g. a configuration in a bare repository, user rights. The refs/meta/config namespace was introduced resp gets 
   used by Gerrit (software)[clarification needed][45]
   tags
   see above.

Common Usage

create a new repository
create a new directory, open it and perform a
git init
to create a new git repository.

checkout a repository
create a working copy of a local repository by running the command
git clone /path/to/repository
when using a remote server, your command will be
git clone username@host:/path/to/repository

workflow
your local repository consists of three "trees" maintained by git. the first one is your Working Directory 
which holds the actual files. the second one is the Index which acts as a staging area and finally the HEAD 
which points to the last commit you've made. 

add & commit
You can propose changes (add it to the Index) using
git add <filename>
git add *
This is the first step in the basic git workflow. To actually commit these changes use
git commit -m "Commit message"
Now the file is committed to the HEAD, but not in your remote repository yet.

pushing changes
Your changes are now in the HEAD of your local working copy. To send those changes to your 
remote repository, execute
git push origin master
Change master to whatever branch you want to push your changes to.
If you have not cloned an existing repository and want to connect your repository to a remote 
server, you need to add it with
git remote add origin <server>
Now you are able to push your changes to the selected remote server

update & merge
to update your local repository to the newest commit, execute
git pull
in your working directory to fetch and merge remote changes.
to merge another branch into your active branch (e.g. master), use
git merge <branch>
in both cases git tries to auto-merge changes. Unfortunately, this is not always possible and results in conflicts. 
You are responsible to merge those conflicts manually by  editing the files shown by git. After changing, you need to mark them as merged with
git add <filename>
before merging changes, you can also preview them by using
git diff <source_branch> <target_branch>

replace local changes
In case you did something wrong, which for sure never happens ;), you can replace local changes using the command
git checkout -- <filename>
this replaces the changes in your working tree with the last content in HEAD. Changes already added to the index, 
as well as new files, will be kept.
If you instead want to drop all your local changes and commits, fetch the latest history from the server and point 
your local master branch at it like this
git fetch origin
git reset --hard origin/master

log
in its simplest form, you can study repository history using.. git log
You can add a lot of parameters to make the log look like what you want. To see only the commits of a certain author:
git log --author=bob
To see a very compressed log where each commit is one line:
git log --pretty=oneline
Or maybe you want to see an ASCII art tree of all the branches, decorated with the names of tags and branches:
git log --graph --oneline --decorate --all
See only which files have changed:
git log --name-status
These are just a few of the possible parameters you can use. For more, see git log --help

tagging
it's recommended to create tags for software releases. this is a known concept, which also exists in SVN.
You can create a new tag named 1.0.0 by executing
git tag 1.0.0 1b2e1d63ff
the 1b2e1d63ff stands for the first 10 characters of the commit id you want to reference with your tag. 
You can get the commit id by looking at the...

Decimal <--> Hexadecimal

Hexadecimal	Decimal
    0	          0
    1	          1
    2	          2
    3	          3
    4	          4
    5	          5
    6	          6
    7	          7
    8	          8
    9	          9
    A	          10
    B	          11
    C	          12
    D	          13
    E	          14
    F	          15

Radio station is streaming MP3 audio at 192kbps. How many 500GB harddisks are required in order to archive 8 years of shows?

192 kbps = 192 000 bps 1 536 000 Bps

1500 Kb/s 1.46484375 MB/s

8 years = 2920 days = 70080 hours = 4204800 minutes = 252288000 seconds

172 228608 MB 16 8192 GB 336.384 500GB harddrives

Audio and Images

Audio
In digital audio, 44,100 Hz (alternately represented as 44.1 kHz) is a common sampling frequency. 
Analog audio is recorded by sampling it 44,100 times per second, and then these samples are used 
to reconstruct the audio signal when playing it back.

Images
PNG supports palette-based images (with palettes of 24-bit RGB or 32-bit RGBA colors), grayscale images (with or without alpha channel),
and full-color non-palette-based RGB[A] images (with or without alpha channel). PNG was designed for transferring images on the Internet,
not for professional-quality print graphics, and therefore does not support non-RGB color spaces such as CMYK.

JPEG/JFIF supports a maximum image size of 65,535×65,535 pixels, hence up to 4 gigapixels (for an aspect ratio of 1:1).
JPEG is a commonly used method of lossy compression for digital images, particularly for those images 
produced by digital photography. The degree of  compression can be adjusted, allowing a selectable tradeoff between storage size 
and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality.

---

Compact Disc
Capacity 	Typically up to 700 MiB (up to 80 minutes audio)
Read mechanism 	780 nm wavelength (infrared and red edge) semiconductor laser, 1200 Kibit/s (1×)
Write mechanism 	1200 Kibit/s (1×)

Sampling 4 bit audio (2^4) gives us only 16 values, a far cry from 16-bit audio's 65,536! sample rate. 
Sample rate refers to the number of samples or measurements taken each  second from a recording. 
The typical CD sample rate is 44.1kHz, or 44,100 samples per second.

The bit rate is quantified using the bits per second unit bit/s, often in conjunction with an SI prefix such as "kilo" 
(1 kbit/s = 1000 bit/s), "mega" (1 Mbit/s = 1000 kbit/s), "giga" (1 Gbit/s = 1000 Mbit/s) or "tera" (1 Tbit/s = 1000 Gbit/s).
The non-standard abbreviation "bps" is often used to replace the standard symbol "bit/s", so that, for example, "1 Mbps" is
used to mean one million bits per second.
One byte per second (1 B/s) corresponds to 8 bit/s.

The RGB565 color format is the same as the RGB555 color format, except that 6 bits are used for 
the green value instead of 5. Therefore, all 16 bits are in use. The  organization of the pixels 
in the image buffer is from left to right and bottom up.
RGB888 --> 24-bit RGB (888)

Statistics Lecture One, 02.01.16

Primary Material:
Course Homepage: http://www.cs.ioc.ee/ITKStat
e-Book:           http://onlinestatbook.com/Online_Statistics_Education.pdf

Primary Software
R: https://www.r-project.org/

Introduction to Statistics
Descriptive statistics are used for presenting, organizing and summarizing data. 
Inferential statistics are about drawing conclusions about a population based on data observed in a sample.

Data Analysis Process
Data collection and preparation: Collect Data, prepare codebook, set up structure of data, enter data, screen data for errors
Exploration of data: Descriptive statistics, graphs
Analysis: Explore relationship between variables, compare groups

Python Lecture and Practicum Notes

Lecture 1

---

Get an idea what to do by next week. Ideas:

// 1. Pyglet,pygame or kivy for a game or simulation:
    1.1. MP beat em' up
    1.2. Survival space sim, use webcam for dynamic view
    1.3. Planet rotation simulation
    Check out 
    http://nehe.gamedev.net/
    http://learnpythonthehardway.org/

// 2. WebApp
    2.1. Budget Management with a GUI

// Notes: 
   * Set up RPi web-server
   * Use XMind to map the idea first
   * Run basic website and deploy webapp to it. 
   * Check out RPi components and sensors. 
   * Buy a breadboard.
   * Check out Notepad++

Web App Programming Lecture and Practicum Notes

database: MySQL -- hosts data, indexed
php: Generates html, server side language
Apache: reads php files and over excecution to PHP interpreter
html: Structure and contents of the web page, (dom-tree)
css: styling information
javascript: client side programming, interacts with html
ubuntu: hosts the programs ( packetization, tcp segmentation )

HTTP requests
node.js -- php
ngix -- apache
nchan

http sockets, streaming push module
WAMP for Windows

http://enos.itcollege.ee/phpmyadmin/
PHP and APACHE is there

http://enos.itcollege.ee/~ksaareme to see changes

W3C validation https://validator.w3.org/

Node.js

Stuff about node.js.