lambert_w, a Fortran90 code which evaluates Lambert's W function.
Lambert's W function W(X) satisfies the equation
W(x) * exp ( W(x) ) = x
The function is defined for -1/e <= x. There are two branches, joining at -1/e = x. The lower branch extends from -1/e <= x < 0 The upper branch extends from -1/e <= x The function is also known as the "Omega" function.
In Mathematica, the function can be evaluated by: W = ProductLog [ X ] In MATLAB, W = lambertw ( b, x ) In Python, W = scipy.special.lambertw ( x, b )
The computer code and data files made available on this web page are distributed under the MIT license
lambert_w is available in a Fortran90 version and a MATLAB version and an Octave version and a Python version.
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