Updates:
Status: Accepted
Cc: fredrik....@gmail.com
Labels: Solvers
Comment #1 on issue 2656 by asmeurer: Solve exp(x*log(x) - 1, x)
http://code.google.com/p/sympy/issues/detail?id=2656
You cannot use mpmath functions with symbolic arguments. You need to use a
SymPy function, unless you are just computing a floating point value (I
still recommend using a SymPy function with .evalf(), when possible).
According to
http://docs.sympy.org/0.7.1/modules/mpmath/functions/expintegrals.html?highlight=erfc#mpmath.erfc,
erfc == 1 - erf, so you should instead do
solve(x * ((1.0 / sqrt(2 * pi) * x * sigma) * exp(-0.5 * (log(x) - mu)**2 /
sigma**2)) + 0.5 * (1 - erf((mu - log(x))) / (sigma * sqrt(2))) - 1, x)
(and don't import stuff from mpmath). Unfortunately, this still doesn't
work (NotImplementedError), but if it did work, that would be the way to do
it.
By the way, Fredrik, it seems there is a typo in the docstring for erfc.
The first LaTeX math is not being rendered.
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