Fetching, wrangling and visualising sunrise and sunset data using Python

Previously I showed how it was possible to obtain sunrise and sunset times for a whole year at any location on Earth, from a public source. This time I am going to explain how to fetch that data, clean it up and create graphical visualizations like the one below, all using Python. A Jupyter Notebook is available on GitHub. Such data might even be useful in, for example, simulation of solar power generation....

February 2, 2018 · Simon

How to get Sunrise and Sunset times for data analysis

jinsngjung / Pixabay Today is 2nd January and the days are getting longer again. I was thinking about sunrise and sunset times and wondering if I should do some data analysis and plotting of these to visualize how they change over the course of a year. Of course, the first step is to get a suitable data set. You can get a data set of sunrise and sunset times from this page on the US Naval Observatory (USNO) website....

January 2, 2018 · Simon

Configuring KNIME to work with Python 2.7.x on Windows

UPDATE: These days it is recommended to use Python3 instead of Python2 Apparently it is tricky to get Python integration working in the KNIME Analytics Platform. If you read the official guide too quickly you can miss some critical information at the bottom of the page. I was getting an error complaining that the google.protobuf library was missing even though I thought that I had everything installed correctly: Library google.protobuf is missing, required minimum version is 2....

August 23, 2017 · Simon

Successfully clearing ports in Salome (Code ASTER)

Figure: Building a geometry in the Salome graphical user interface (GUI). How Salome tracks ports When Salome is starting up, it checks for free ports on your system using a few built-in Python scripts. Then when you close Salome those ports should be freed up again for the next one. This has a number of uses, but one reason is to stop multiple instances of Salome trying to use the same port at once....

June 1, 2017 · Simon

Parallelization in Python example with joblib

It can be ridiculously easy to parallelize code in Python. Check out the following simple example: import time from joblib import Parallel, delayed # A function that can be called to do work: def work(arg): print "Function receives the arguments as a list:", arg # Split the list to individual variables: i, j = arg # All this work function does is wait 1 second... time.sleep(1) # ... and prints a string containing the inputs: print "%s_%s" % (i, j) return "%s_%s" % (i, j) # List of arguments to pass to work(): arg_instances = [(1, 1), (1, 2), (1, 3), (1, 4)] # Anything returned by work() can be stored: results = Parallel(n_jobs=4, verbose=1, backend="threading")(map(delayed(work), arg_instances)) print results Output:...

April 3, 2017 · Simon

How to get up-to-date Python packages without bothering your cluster admin

If you have ever been stuck as a user on an out-of-date cluster without root access it can be frustrating to ask the admin guy to install packages for you. Even if they respond, by the time they get round to it you might have moved onto something else. The moment could be gone. Luckily, as far as Python is concerned, the pyenv project allows users to install their own local Python version or even assign different versions to different directories/projects....

September 1, 2016 · Simon

Plotting multivariate data with Matplotlib/Pylab: Edgar Anderson’s Iris flower data set

The problem of how to visualize multivariate data sets is something I often face in my work. When using numerical optimization we might have a single objective function and multiple design variables that can be represented by columnar data in the form {x1, x2, x3, … xn, y} a.k.a. NXY. With design spaces of more than a few dimensions it is difficult to visualize them in order to estimate the relationship between each independent variable and the objective, or perform a sensitivity study....

August 31, 2016 · Simon

The new default colormap for matplotlib is called “viridis” and it’s great!

It’s probably not news to anyone in data visualization that the most-used “jet” colormap (sic) (sometimes referred to as “rainbow”) is a bad choice for many reasons. Doesn’t work when printed black & white Doesn’t work well for colourblind people Not linear in colour space, so it’s hard to estimate numerical values from the resulting image The Matlab team recently developed a new colormap called “parula” but amazingly because Matlab is commercially-licensed software no-one else is allowed to use it!...

April 6, 2016 · Simon

5 Tips for making finite element models with Salome

Salome is an open source software package used to create geometric models and finite element meshes for use in numerical simulations. It is also able to perform its own numerical simulations and has post-processing capabilities built in. Here are my 5 tips for anyone who is interested in using Salome for model and mesh creation. 1. Practice manually first This goes without saying. Although Salome has a powerful Python-based scripting capability, it is worth practicing with manual model generation....

August 15, 2015 · Simon

Reading an OpenOffice spreadsheet into Python

Sometimes the best way to manage simulation output data is in a spreadsheet. Or the data you want to use is already in a spreadsheet. Before reading it into Python for numerical analysis or plotting, or reading into xmgrace to plot, etc, it is normal to export the spreadsheet to a CSV or tab-separated file. But then you have two files. And if you do something in the spreadsheet you have to export it again and this is inefficient....

February 28, 2014 · Simon