Python Scipy Error Function
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2/sqrt(pi)*integral(exp(-t**2), t=0..z). Parameters:x python erfc : ndarray Input array. Returns:res : ndarray The values of module 'scipy' has no attribute 'special' the error function at the given points x. See also erfc, erfinv, erfcinv Notes The cumulative of the unit normal distribution
Scipy Erfinv
is given by Phi(z) = 1/2[1 + erf(z/sqrt(2))]. References [R200]http://en.wikipedia.org/wiki/Error_function [R201]Milton Abramowitz and Irene A. Stegun, eds. Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables. New York: Dover, 1972. http://www.math.sfu.ca/~cbm/aands/page_297.htm [R202]Steven G. Johnson, Faddeeva W function implementation. http://ab-initio.mit.edu/Faddeeva Previous topic scipy.special.multigammaln Next topic scipy.special.erfc © Copyright 2008-2009, The Scipy community. Last updated on May 11, 2014. Created using Sphinx 1.2.2.
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Python Error Handling Best Practices
Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 6.2 million programmers, just like you, helping each other. Join https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.special.erf.html them; it only takes a minute: Sign up command for inverse ERF function in python [closed] up vote 7 down vote favorite What is the command to calculate Inverse Error function (erf) of a function in a python and which module is needed to import? python python-2.7 python-3.x numpy share|improve this question asked Jul 7 '15 at 10:37 Naitik http://stackoverflow.com/questions/31266249/command-for-inverse-erf-function-in-python Mathur 442 closed as unclear what you're asking by jonrsharpe, ekad, cel, HaveNoDisplayName, Soner Gönül Jul 7 '15 at 14:50 Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question.If this question can be reworded to fit the rules in the help center, please edit the question. add a comment| 2 Answers 2 active oldest votes up vote 10 down vote For the inverse error function, scipy.special has erfinv: http://docs.scipy.org/doc/scipy/reference/generated/scipy.special.erfinv.html#scipy.special.erfinv In [4]: from scipy.special import erfinv In [5]: erfinv(1) Out[5]: inf In [6]: erfinv(0.4) Out[6]: 0.37080715859355784 share|improve this answer answered Jul 7 '15 at 10:41 xnx 11.1k31541 add a comment| up vote 0 down vote I suggest to use scipy, a library that uses numpy. the module you need to import to use is erfinv: from scipy.special import erfinv Scipy is a key player for numerical software in Python. But it might be a little challenging getting
19 January 2009 by John The question came up on StackOverflow this morning how to compute the error function erf(x) in Python. The standard answer for how to compute anything numerical in Python is "Look in SciPy." However, this person didn't want to take on the dependence on SciPy. I've seen variations on http://www.johndcook.com/blog/2009/01/19/stand-alone-error-function-erf/ this question come up in several different contexts lately, including questions about computing the normal distribution function, so I thought I'd write up a solution.Here's a Python implementation of erf(x) based on formula 7.1.26 from https://www.quora.com/What-is-the-command-to-calculate-the-inverse-erf-of-a-function-in-a-Python-and-which-module-is-needed-to-import A&S. The maximum error is below 1.5 × 10-7.import math def erf(x): # constants a1 = 0.254829592 a2 = -0.284496736 a3 = 1.421413741 a4 = -1.453152027 a5 = 1.061405429 p = 0.3275911 # Save the sign error function of x sign = 1 if x < 0: sign = -1 x = abs(x) # A & S 7.1.26 t = 1.0/(1.0 + p*x) y = 1.0 - (((((a5*t + a4)*t) + a3)*t + a2)*t + a1)*t*math.exp(-x*x) return sign*yThis problem is typical in two ways: A&S has a solution, and you've got to know a little background before you can use it.The formula given in A&S is only good for python scipy error x ≥ 0. That's no problem if you know that the error function is an odd function, i.e. erf(-x) = -erf(x). But if you're an engineer who has never heard of the error function but needs to use it, it may take a while to figure out how to handle negative inputs.One other thing that someone just picking up A&S might not know is the best way to evaluate polynomials. The formula appears as 1 - (a1t1 + a2t2 + a3t3 + a4t4 + a5t5)exp(-x2), which is absolutely correct. But directly evaluating an nth order polynomial takes O(n2) operations, while the factorization used in the code above uses O(n) operations. This technique is known as Horner's method. Categories : Computing Math PythonTags : Python Special functionsBookmark the permalink Post navigationPrevious PostDraw a bigger pictureNext PostStand-alone normal (Gaussian) distribution function 14 thoughts on “Stand-alone error function erf(x)” Sergey Fomel 19 January 2009 at 16:21 erf is actually a standard function in C "math.h"For some reason, it is not included in Python's math module but, if you have SWIG, it is easy to write a SWIG wrapper for it. An example on a Linux machine: bash$ cat erf.i %module erf #include double erf(double); bash$ swig -o erf_wrap.c -python erf.i bash$ gcc -o erf_wr
ProgrammingWhat is the command to calculate the inverse erf of a function in a Python and which module is needed to import?UpdateCancelAnswer Wiki1 Answer Mohsen NabianWritten 22w agoFor the inverse error function, scipy.special has erfinv:http://docs.scipy.org/doc/scipy/...In [4]: from scipy.special import erfinv In [5]: erfinv(1) Out[5]: inf In [6]: erfinv(0.4) Out[6]: 0.37080715859355784 125 ViewsView More AnswersRelated QuestionsWhen trying to import and execute a function within a Python module from a C++ executable, how can I pass in the directory where the module is...Is it allowed in Python to import an entire module and some functions from said module separately?How do I control functions which can be imported from a pure module in Python?Can I know what all modules, classes, and their functions are available in Python right with some command or function like dir(