R
Python or Julia?
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Julia people how good is symbolics.jl compared to SymPy?
How good is sympy compared to Matlab?
The Julia ecosystem is not yet mature relative to Python, and that is by far the most important aspect in the choice of a platform/language. Just look at the state of ML in Python. Interpreter speed is moot in most cases because the underlying libraries are native code, which will always be faster than pure Julia.
If you really need custom, high speed code write the relevant portions and C and interface from Python to exploit all the data exploration, graphics, report generation Python goodies.