Installation

Caveat: These instructions are old (circa Julia 0.5) The same ideas apply, but they need updating. You can probably find a better reference now.

Before you can use Laplacians, you need Julia. So, we'll begin with instructions for installing Julia. I (Dan S.) found that it worked best if I installed Python first. So, I'll suggest that you do the same.

All of these instruction assume you are using a Mac.

Python

Install python. I recommend the anaconda distribution https://www.continuum.io/downloads.

Once you install python, you are going to want two packages: a plotting package that Julia will use, and jupyter notebooks for interacting with Julia. Install them like

conda install matplotlib
conda install mathjax
conda install jupyter

Julia

You can get Julia from http://julialang.org/. If you are using a Mac, you may wish to create a symnolic link to the Julia executable so that you can call it from a terminal. For example, you can do this like:

cd /usr/local/bin/
ln -s julia /Applications/Julia-0.5.app/Contents/Resources/julia/bin/julia

Once you have this, you will want Julia notebooks. To install this, run julia and type

julia> Pkg.add("IJulia")
julia> using IJulia

This will install the package, and put the current julia kernel into jupyter. In the future, you can launch the Julia notebook by typing (in a terminal)

jupyter notebook

Most users will also want to install PyPlot, if you did not already. To do that, type

Pkg.add("PyPlot")

Laplacians

In theory, all you need to do now is type either

julia> Pkg.add("Laplacians")

To use the package, you then type

julia> using Laplacians

The one catch is with the functions for drawing graphs. These require PyPlot. If you did not install it before typing Pkg.add("PyPlot"), then you can either install it now or disable the plotting routines in Laplacians.

If you do not want to load PyPlot, then either set the environment variable LAPLACIANS_NOPLOT to true in bash, like

$ export LAPLACIANS_NOPLOT=true

or, set the variable inside Julia, like

julia> LAPLACIANS_NOPLOT = true

before typing using Laplacians. Similarly, you can avoid loading PyAmg by setting

julia> LAPLACIANS_NOAMG = true

(note that these are not the same variable: the environment variable in Julia is available as ENV["LAPLACIANS_NOPLOT"]. Actually, defining these variables to anything will have the same effect. So, setting them to false has the same effect as setting them to true.

To see if Laplacians is working, try typing

a = chimera(100,6)
spectral_drawing(a)

a = generalizedNecklace(grid2(6),grid2(3),2)
spectral_drawing(a)