ELKI is described as ': "Environment for Developing KDD-Applications Supported by Index-Structures" is a development framework for data mining algorithms written in Java. It includes a large variety of popular data mining algorithms, distance functions and index structures'. There are more than 10 alternatives to ELKI for a variety of platforms, including Linux, Mac, Windows, Online / Web-based and BSD. The best alternative is GNU Octave, which is both free and Open Source. Other great apps like ELKI are R (programming language) (Free, Open Source), MATLAB (Paid), Scilab (Free, Open Source) and Julia (Free, Open Source).
Octave is a computer program for performing numerical computations which is mostly compatible with MATLAB. It is part of the GNU Project. It is free software under the terms of the GNU General Public License.
MATLAB is a numerical computing environment and programming language. Maintained by The MathWorks, MATLAB allows easy matrix manipulation, plotting of functions and data, implementation of algorithms, creation of user interfaces, and interfacing with programs in other languages.
SageMath is a free open-source mathematics software system licensed under the GPL. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more.
Orange is an open-source, cross-platform data mining and machine learning suite. It features visual programming as intuitive means of combining data analysis and interactive visualization methods into powerful workflows.
RapidMiner (Community edition) is a data mining software. It was formerly known as "YALE". You can use RapidMiner as a stand-alone application for data analysis, or integrate it as a data-mining engine into your own products.