When comparing FreeMat vs SageMath, the Slant community recommends SageMath for most people. In the question“What are the best free Matlab alternatives?” SageMath is ranked 2nd while FreeMat is ranked 4th. The most important reason people chose SageMath is:
Jupyter Notebook supports Sagemath Kernel.
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Pros
Pro Free open-source software. Compares favorably to Mathematica. INCLUDES Maxima in distro. Web-based CoCalc is excellent app based on Sagemath.
Jupyter Notebook supports Sagemath Kernel.
Pro Versatile
Though SageMath depends on other software packages for the heavy lifting, SageMath offers a centralized interface for working with many subfields of mathematics.
Cons
Con Outdated
The code-base has not been actively maintained since 2013.
Con Incoherent design
Con Poor documentation
Con Bloated
SageMath does not do much mathematics by itself. Instead, it depends on many CAS and non-CAS software packages, which it calls based on the desired operations. Installing SageMath pulls in all those packages as mandatory prerequisites. There is no lightweight GUI either.