On colormaps

Problems with the (old) standard colormap in Matlab are widely known. Even MathWorks addressed this issue after changing the default colormap in this blog post. But there are several other sources that discuss this issue or provide better colormaps. Most of them just a short Google search away (e.g. here, here or here).

The de facto standard source for good colormaps is ColorBrewer developed by Cynthia Brewerbased on the research of Dr. Cynthia Brewer. To use these maps in Matlab, you can use BrewerMap by DrosteEffect.

To summarize some of the different colormaps, I chose some typical numerical results that I often have to visualize. These are visualized with different ColorBrewer maps, as well as with jet for comparison.

The first example is the checkerboard test case. A source is placed in the middle of the domain and emits radiation in a heterogeneous environment. As for all further pictures: everything is the same but the colormap. The checkerboard results are shown below.

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Analyzing Telegram chats with R and Matlab

I am using Telegram a lot for chatting. Since it is possible to export the chat history with everyone you have been chatting with I wanted to create a word cloud featuring the most common words with my chat partners.

I use several tools for this. There is telegram-history-dump which itself uses telegram-cli for exporting the chat history. Then I use Matlab for some postprocessing (or preprocessing, depending on how you view it) to bring the dumped output in a (for me) manageable form. Lastly I use R to generate a word cloud like the one at the top of this post.

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Code for the rSN method

The code can be found here. Below is the documentation that you also find on the linked website.

We implement the rSN method. This is a modification of the standard SN method that mitigates ray-effects by rotation of the quadrature step after each time step. An interpolation procedure is required which furthermore requires different (non-tensorized) quadrature sets. All these aspects are implemented in this code with Julia.
The two figures below demonstrate the effect that the rotation of the angular quadrature set has on the overall solution quality. In the first picture we see ray-effects for the line-source problem. In the second picture these effects were mitigated due to the rotation.

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