====== Starting a Julia notebook ======

A Julia notebook is a system that combines mathematical text, executable Julia code, and graphical output within a web browser. If you have Julia running on a laptop or UNH computer, you can start a notebook as follows

Note: you will have to do all these steps //only the first time// you run a Julia notebook. After that you can just start with step 5, ''using IJulia''. 

**1.** Download a Julia notebook file to your computer. Let's start with notebooks from [[http://sistemas.fciencias.unam.mx/~dsanders/|David Sanders]]' [[https://github.com/dpsanders/hands_on_julia|Hands-on Julia]] tutorial. You can download them from the previous link or get them here: 

  * {{:gibson:teaching:fall-2016:math753:hands_on_julia:1._numbers_variables_and_basic_functions.ipynb|1. Numbers, variables and basic functions.ipyn}}
  * {{:gibson:teaching:fall-2016:math753:hands_on_julia:2._iteration_-_ranges_vectors_and_conditionals.ipynb|2. Iteration - ranges, vectors and conditionals.ipynb}}

**2.** Start the Julia REPL by clicking the executable or directly from the command line. 
<code>
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: http://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.4.6 (2016-06-19 17:16 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-unknown-linux-gnu

julia> 
</code>

**3.** At the Julia prompt, type ''Pkg.add("IJulia")''. This tells Julia to download and install the IJulia notebook software onto the computer. 

<code julia>
julia> Pkg.add("IJulia")
INFO: Nothing to be done                                                                        
INFO: METADATA is out-of-date — you may not have the latest version of IJulia                   
INFO: Use `Pkg.update()` to get the latest versions of your packages                            
julia>
</code>                                               

**4.** At the Julia prompt, type ''Pkg.update()''. This tells Julia to download and install any required software updates. This might take a while and print out lots of download & install information.

<code>
julia> Pkg.update()
INFO: Updating METADATA...
INFO: Updating cache of ColorTypes...
INFO: Updating cache of BinDeps...
INFO: Updating cache of ZMQ...
INFO: Updating cache of IJulia...
INFO: Updating cache of URIParser...
INFO: Updating cache of Conda...
INFO: Updating cache of HttpCommon...
....and many more such messages...

julia>
</code>

**5.** At the Julia prompt, type ''using IJulia''. This tells Julia to load the IJulia module into your active Julia session. 
<code>
julia> using IJulia
INFO: Recompiling stale cache file /home/gibson/.julia/lib/v0.4/IJulia.ji for module IJulia.
INFO: Recompiling stale cache file /home/gibson/.julia/lib/v0.4/ZMQ.ji for module ZMQ.
INFO: Recompiling stale cache file /home/gibson/.julia/lib/v0.4/Nettle.ji for module Nettle.

julia> 
</code>

**6.** At the Julia prompt, type ''notebook(dir=homedir())''. This tells Julia to start an IJulia notebook in a browser, either starting up a new browser, if you don't have one running, or as a new tab in an existing browser. The ''dir=homedir()'' argument tells Julia to start the notebook in your home directory (folder), rather than 

<code>
julia> notebook(dir=homedir())
</code>

You should be able to naviagate to wherever you downloaded the Julia notebook file. The browser window will look somethign like this, listing the Julia notebooks you downloaded.

 {{ :gibson:teaching:fall-2016:math753:hands_on_julia:jupyter1.jpg?800 |}}


**6.** Click on "Numbers, variables, and basic functions.ipynb" in the browser. That'll start the interactive Julia notebook session. 

 {{ :gibson:teaching:fall-2016:math753:hands_on_julia:jupyter2.jpg?800 |}}

**7.** At this point you can click on and modify anything in the Julia notebook. Try clicking on the line that read ''typeof(10)'' and then hitting "shift-return" or "shift-enter" to execute the ''typeof(10)'' statement. i.e. to make Julia evaluate the expression ''typeof(10)'' and respond with the result.