Here is another great MATLAB-based website, the one about recurrence plots by my colleague and long-term collaborator Norbert Marwan from Potsdam Institute for Climate Impact Research (PIK). Recurrence plots for the analysis of complex systems are popular in many fields such as climate science, flow mechanics and medicine. Continue reading “Cross Recurrence Plot Toolbox”
About me
Here is a short outline of my research and teaching at the U Potsdam, Germany, and elsewhere, with emphasis on the use of MATLAB in earth sciences.
The MATLAB® / LEGO® MINDSTORMS® Model of a Moving Satellite
This was one of my first MATLAB® / LEGO® MINDSTORMS® projects: the model of a moving satellite. Three exercises have been developed from this, which I will shortly provide in the member area with solutions.
Continue reading “The MATLAB® / LEGO® MINDSTORMS® Model of a Moving Satellite”
MRES Exercise #13 Removing NaNs from all Variables in the Workspace
I often had the problem that I had a lot of variables of different types and dimensions in the workspace, which contain either NaN or another no data identifier to identify data gaps. If you want to use this data with other software tools, such as ArcGIS, NaNs must be replaced by other no-data identifiers. The other way round, if you work with digital terrain models (such as the SRTM data set, see Chapter 7.5 of the MRES book), you have to place -32768 (i.e. the lowest possible value of data of the signed integer 16 bit or int16 format) by NaNs in order to use them with MATLAB. As an example, we first create some random variables with NaNs:
clear A = rand(3,3); A(2,1) = NaN; BC = rand(2,4); BC(2,2) = NaN; DE = rand(1,2); DE(1,1) = NaN; FG = rand(3,2); FG(2,2) = NaN; HJ = 'A character array';
We can display the value of the variables in the Command Window by typing
A, BC, DE, FG, HJ
resulting in the output
A = 0.9797 0.2581 0.2622 NaN 0.4087 0.6028 0.1111 0.5949 0.7112 BC = 0.2217 0.2967 0.4242 0.0855 0.1174 NaN 0.5079 0.2625 DE = NaN 0.0292 FG = 0.9289 0.5785 0.7303 NaN 0.4886 0.4588 HJ = A character array
Here is the script to replace all NaNs by the value -999. It first stores the list of variables from the output of who in the array variables. Then it uses eval to execute the MATLAB expression in the variable names, i.e. it gets the values of the variables by calling them, and stores the variables in the array v. Then it locates the NaNs using isnan and replaces the NaNs by -999. Then it assigns the new arrays to the variables variables. Finally it displays the new values of the variables using eval.
variables = who; for i = 1 : size(variables,1) v = eval(variables{i}); v(isnan(v)==1) = -999; assignin('base',variables{i},v); eval(variables{i}) end
resulting in the output
A = 0.1690 0.6477 0.2963 -999.0000 0.4509 0.7447 0.7317 0.5470 0.1890 BC = 0.6868 0.3685 0.7802 0.9294 0.1835 -999.0000 0.0811 0.7757 DE = -999.0000 0.4359 FG = 0.4468 0.5108 0.3063 -999.0000 0.5085 0.7948 HJ = A character array
You can use the script to replace any other value by another value.
The MATLAB® / LEGO® MINDSTORMS® Shopping List
So it all started. I was an invited speaker at the MATLAB Expo 2016 in Munich with a lecture on “Dust storms, blackouts and 50°C in the shade: with MATLAB in the cradle of humankind“. One of Keynote Lectures was held by Dr. Rainer Stetter of ITQ, “Industry 4.0 – Risks and Opportunities”, who talked, among other things, about the European Hi5 Hackathon 2016 with MATLAB and LEGO MINDSTORMS. I wondered how I could use the connection of MATLAB and LEGO MINDSTORMS, using the hardware support of The MathWorks in my shortcourses on geoscientific data analysis and future editions of the textbooks.
Continue reading “The MATLAB® / LEGO® MINDSTORMS® Shopping List”
Calculating the Continuous 1-D Wavelet Transform with the new Function cwt, Part 1
In MATLAB R2016b, the function to calculate a continuous 1D wavelet transform has been replaced by a new function, unfortunately with the same name. Here is a great example why I think that this blog is very useful: Here I can let you know how I would modify the script of Chapter 5.8 of MRES and ask for your comments on it, long before the 5th edition of MRES will be published.
All about the Books
For those of you who do not already know the two Springer books, here is a summary of the books, the available editions, the electronic supplement and errata files.
TopoToolbox
Here is one of my most favorite MATLAB-based earth science toolboxes: the TopoToolbox by Wolfgang Schwanghart. TopoToolbox is a program for the analysis of digital elevation models (DEMs). It’s free and open source (as long as you have MATLAB).