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Questions tagged [inverse]

In mathematics, a function y=f(x) tells us how to map input x to output y. Inverting a function (or an operator) is attempting to find a function f¯¹ that maps y to x, such that x=f¯¹(f(x)).

In mathematics, a function y = f(x) tells us how to map input x to output y. Inverting a function (or an operator) is attempting to find a function f -1 that maps y to x, such that x = f -1( f(x) ).

It is not always possible to find the inverse map, and sometimes it does not even exist.

One of the most common inverse problems is inverting an n × n matrix: only square matrices A with det(A) ≠ 0 have an inverse matrix A-1. See .

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Reverse Spectrogram A La Aphex Twin in MATLAB

I'm trying to convert an image into an audio signal in MATLAB by treating it as a spectrogram as in Aphex Twin's song on Windowlicker. Unfortunately, I'm having trouble getting a result. Here it what I have at the moment: function signal =…
Scott
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Do I Have to Manually Set a Core Data Object's Inverse Relationship in Code on the iPhone

I am new to core data so please excuse me if I get some of the terms wrong. I have several objects in my xcdatamodel file. They are all inter connected with relationships and inverse relationships. If I connect two of these objects with the…
iHorse
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Hibernate Inverse attribute

I am creating a one-to-many relationship. so, i have a parent and a child. The cascade attribute is set to all. I was wondering, if we consider the following piece of code: Parent p = (Parent) session.load(Parent.class, pid); Child c = new…
TimeToCodeTheRoad
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Inverse sqrt for fixed point

I am looking for the best inverse square root algorithm for fixed point 16.16 numbers. The code below is what I have so far(but basically it takes the square root and divides by the original number, and I would like to get the inverse square root…
Jonathan
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Fast algorithm to invert a boolean sum of products

I'm trying to implement a very very fast boolean expression engine. I'm using it to represent states in very large state spaces, so I need it to handle as many operations per second as possible. At the very base of this engine is a sum of products.…
Ned Bingham
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Algorithm for computing the inverse of a polynomial

I'm looking for an algorithm (or code) to help me compute the inverse a polynomial, I need it for implementing NTRUEncrypt. An algorithm that is easily understandable is what I prefer, there are pseudo-codes for doing this, but they are confusing…
Mohammad Sepahvand
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local inverse of a neural network

I have a neural network with N input nodes and N output nodes, and possibly multiple hidden layers and recurrences in it but let's forget about those first. The goal of the neural network is to learn an N-dimensional variable Y*, given N-dimensional…
user2118903
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Inverse function in Scala

Is there a way to express the inverse of any function in Scala? For example if I have a function f like this: (x: Int) => x + 1 I would like to be able write an inverse function g like: (f(x): Int) => x // not a valid scala syntax or (x: Int) =>…
Loic
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How to get inverse operation of flatten for objects using jq?

Through another SO thread, I found how to "flatten" JSON using jq. I am looking how to do the inverse, i.e., "unflatten" it. Original JSON has mixed levels in the hierarchy, e.g.: { "X1": { "X1o1": { "X1o1o1": "abc", "X1o1o2":…
laracee
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Is there a logit function in tensorflow?

Is there a logit function in tensorflow, i.e. the inverse of sigmoid function? I have searched google but have not found any.
Larry Xu
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How to invert double[,] in C#

I am making a program, where I need to calculate linear regression, but I got stuck at inversion of a matrix. I have double[,] location = new double[3,3]; It was then filled with numbers, but then I do not know, how to count the inverse matrix for…
Štěpán Šubík
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How to do inverse real to real FFT in FFTW library

I'm trying to do some filtering with FFT. I'm using r2r_1d plan and I have no idea how to do the inverse transform... void PerformFiltering(double* data, int n) { /* FFT */ double* spectrum = new double[n]; …
Kirill Dubovikov
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Singular matrix - python

The following code shows a problem of singularity of a matrix, since working in Pycharm I get raise LinAlgError("Singular matrix") numpy.linalg.linalg.LinAlgError: Singular matrix I guess the problem is K but I cannot understand exactly how: from…
johnhenry
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Plot inverse colors in Matlab?

I'm plotting on top of an image in Matlab. Sometimes, I can't see what's being plotted because the color of the image underneath is too close to the color of the image at the same location. I could just always change the color of the plot (e.g.…
Benjamin Oakes
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inverse square root in Python

Does any Python library offer a function that implements the "fast inverse square root" algorithm described in following link? http://en.wikipedia.org/wiki/Fast_inverse_square_root Perhaps numpy/SciPy?
Andreas Gschossmann
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