# The NumeRe Blog

## News, examples and everything else that comes to our minds

During our work on NumeRe, we are always coming into contact with exciting or interesting topics. These can be example data analyses illustrating new features or trivia.

Want to publish something about NumeRe? We accept contributions from the community. Get in touch with us via Discord.

## NumeRe is "Community Choice"

After more than 10,000 downloads of NumeRe, we have been awarded the "Community Choice" badge by SourceForge. We would like to thank all our loyal supporters. The next step is now to reach 50,000 downloads.

## How to Find Edges in Images

Edge detection is a common task in image processing. It is used to recognize the positions of structures, to examine motion sequences or, in general, simply to separate the foreground from the background. There are very advanced methods for this, but we want to focus on the fact that you can already achieve good results with simple options.

## 10 Years of NumeRe

Wow. Is it that far already? October 2013 to October 2023. That's 10 years and a wild ride.

What started in 2013 as a mini-project for student education has become a global player in numerics programs in 10 years. Well, almost. NumeRe is available worldwide and free, but we are still working on beating the commercial competition...

## How to Access Data from the Net

In many cases, data that one would like to process is not on the local machine, but is located in an online repository. This can either be a file host or it is an API, through which you can get the desired and possibly even pre-filtered data by means of a URL. We'll show how to get to it, because it's an easy to understand example, with the data of the DAX, which we get from the Yahoo Finance API.

## The Fall of StackOverflow

A few days ago, the news went through social media that StackOverflow was struggling with ChatGPT and that because of that, visits, pageviews, and interactions had dropped sharply. Although the trend is undeniable based on the available data, the question is whether the connection between the release of ChatGPT and the rapid decrease in StackOverflow's visitors is actually causal. Or are we much more trying to confirm our own expectation?

## How to Visualize the Orbitals of Atoms

Atomic orbitals are a well-known concept that is already taught in chemistry classes at secondary schools. Unfortunately, they often do not go into detail about what they actually are and how they are calculated. Of course, we cannot provide a quantum mechanical derivation here, but we can highlight a few interesting aspects nonetheless.

## How Sea Shells Show the Beauty of Maths

Mathematics scares many people away, which is actually a shame considering the exhilaratingly beautiful images it can create. For example, the shell seen above, which could possibly belong to a sea snail. Even if this structure looks highly complex and one cannot imagine that this could be represented by mathematical functions, these are "comparatively" simple expressions which only describe a coordinate transformation.

If you want to try it out: just copy the following (very long) line into the NumeRe terminal and execute it.

surf (0.1-(1-y/2)/5*(1+cos(_pi*x)) * cos(_2pi*y), (0.1-(1-y/2)/5*(1+cos(_pi*x))) * sin(_2pi*y), y/4-(1-y/2)/5 * sin(_pi*x), norm((0.1-(1-y/2)/5*(1+cos(_pi*x))) * sin(_2pi*y),(0.1-(1-y/2)/5*(1+cos(_pi*x))) * cos(_2pi*y)) -set [-1:1, -1:1] coords=parametric light colorscheme=polarity colormask rotate=80,-150 box nocolorbar

## Why Measured Variables Extremely Rarely Depend on Only one Parameter

How nice it would be if the correlations in the data we analyze every day were linear and independent of other influencing variables. However, the above example immediately shows that this does not correspond to reality. The numbers of rented bicycles in the city of Seoul in 2018 are shown. The two axes describe the measured temperature and the respective time of day. The graph on the bottom left shows the number of rented bicycles in a color scale, while the two surrounding bar charts sum up the data orthogonal to the axes respectively.

This graph is generated with hist2d in the following way:

hist2d data(:,{4,3,2}) -sum bins=23 xlabel="Temperature" ylabel="Hour" zlabel="Rented bikes"

As can be clearly seen, there are dependencies on the measured daytime temperature with a maximum around 24 °C, as well as dependencies on the time of day, the maxima of which are around 8 am and 6 pm. This, of course, corresponds to the common start and end times of work for many people who apparently like to use rented bicycles for commuting here.

Thus, if one wants to make a prediction for a demand for a service, it is important to know and be able to quantify all the variables influencing this demand.

## We're a Rising Star

NumeRe was awarded with the "Rising Star" achievement by SourceForge, because we jumped over the 100 monthly downloads threshold. We're very thankful to all our supporters and praise them for their lasting effort in pushing us further.

## Achievement Unlocked

Since a few days we have cracked the magic 1000 downloads mark. NumeRe is obviously on the triumphant march and will soon have won its own place in the ranks of the established numeric programs. At least we hope so ...

Meanwhile, in the style of the current game software, we decided to create unlockable Achievements that we can get for NumeRe. Of course, we have already completed a sensibly chosen part of it, but the rest is still to be done and will of course be targeted by us in the future.

You can also help us with one part: we are still missing reviews on SourceForge to unlock the next Achievement. If you want to tell us and/or the rest of the world your opinion about NumeRe, don't hesitate to do so on SourceForge.

Otherwise: Achievement unlocked: you got the first k!