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  2. Negative relationship - Wikipedia

    en.wikipedia.org/wiki/Negative_relationship

    A negative relationship between two variables usually implies that the correlation between them is negative, or — what is in some contexts equivalent — that the slope in a corresponding graph is negative. A negative correlation between variables is also called inverse correlation. Negative correlation can be seen geometrically when two ...

  3. Sigmoid function - Wikipedia

    en.wikipedia.org/wiki/Sigmoid_function

    A sigmoid function refers specifically to a function whose graph follows the logistic function. It is defined by the formula: σ {\displaystyle \sigma (x)= {\frac {1} {1+e^ {-x}}}= {\frac {e^ {x}} {1+e^ {x}}}=1-\sigma (-x).} In many fields, especially in the context of artificial neural networks, the term "sigmoid function" is correctly ...

  4. Inverse-Wishart distribution - Wikipedia

    en.wikipedia.org/wiki/Inverse-Wishart_distribution

    see below. In statistics, the inverse Wishart distribution, also called the inverted Wishart distribution, is a probability distribution defined on real-valued positive-definite matrices. In Bayesian statistics it is used as the conjugate prior for the covariance matrix of a multivariate normal distribution.

  5. Discrete Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Discrete_Fourier_transform

    Fourier transform (bottom) is zero except at discrete points. The inverse transform is a sum of sinusoids called Fourier series. Center-right: Original function is discretized (multiplied by a Dirac comb) (top). Its Fourier transform (bottom) is a periodic summation (DTFT) of the original transform. Right: The DFT (bottom) computes discrete ...

  6. Cayley graph - Wikipedia

    en.wikipedia.org/wiki/Cayley_graph

    The Cayley graph of the direct product of groups (with the cartesian product of generating sets as a generating set) is the cartesian product of the corresponding Cayley graphs. [3] Thus the Cayley graph of the abelian group with the set of generators consisting of four elements (,), (,) is the infinite grid on the plane , while for the direct ...

  7. Bode plot - Wikipedia

    en.wikipedia.org/wiki/Bode_plot

    Definition. The Bode plot for a linear, time-invariant system with transfer function ( being the complex frequency in the Laplace domain) consists of a magnitude plot and a phase plot. The Bode magnitude plot is the graph of the function of frequency (with being the imaginary unit). The -axis of the magnitude plot is logarithmic and the ...

  8. Zipf's law - Wikipedia

    en.wikipedia.org/wiki/Zipf's_law

    The lower plot shows the remainder when the Zipf law is divided away. It shows that there remains significant pattern not fitted by Zipf law. A plot of the frequency of each word as a function of its frequency rank for two English language texts: Culpeper's Complete Herbal (1652) and H. G. Wells's The War of the Worlds (1898) in a log-log scale.

  9. Inverse function - Wikipedia

    en.wikipedia.org/wiki/Inverse_function

    A function f and its inverse f −1. Because f maps a to 3, the inverse f −1 maps 3 back to a. In mathematics, the inverse function of a function f (also called the inverse of f) is a function that undoes the operation of f. The inverse of f exists if and only if f is bijective, and if it exists, is denoted by.