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Topic: Logistic function

Related Topics

Sigmoid curve

Generalised logistic curve

Exponential growth

Logistic regression

Logistic map

Logistic curve

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	NationMaster - Encyclopedia: Sigmoid function
		Graph of example function, The mathematical concept of a function expresses the intuitive idea of deterministic dependence between two quantities, one of which is viewed as primary (the independent variable, argument of the function, or its input) and the other as secondary (the value of the function, or output).
		Logistic curve, specifically the sigmoid function A logistic function or logistic curve models the S-curve of growth of some set P. The initial stage of growth is approximately exponential; then, as competition arises, the growth slows, and at maturity, growth stops.
		Sigmoid functions are often used in neural networks to introduce nonlinearity in the model and/or to clamp signals to within a specified range.
	www.nationmaster.com /encyclopedia/Sigmoid-function (1388 words)

	Logistic function - Biocrawler
		The logistic function or logistic curve models the S-curve of growth of some set P. The initial stage of growth is approximately exponential; then, as competition arises, the growth slows, and at maturity, growth stops.
		This function is also called the standard logistic function and is often encountered in many technical domains, especially probability, statistics, biomathematics, and economics.
		The logistic function is the inverse of the natural logit function and so can be used to convert the logarithm of odds into a probability; the conversion from the log-likelihood ratio of two alternatives also takes the form of a sigmoid curve.
	www.biocrawler.com /encyclopedia/Verhulst_equation (612 words)

	[No title]
		A logistic activation function is used for the output, with scaling factors determined so that the range encountered in the training set is mapped to a restricted part of the logistic functions (0,1) range (e.g.
		The use of the sum-squared network error function means that points lying far from the others have a disproportionate influence on the position of the hyperplanes used in regression.
		If the loss function is unimodal and has detectable ridges pointing towards the minimum of the function, then this method will proceed with a considerable accuracy towards the minimum of the function.
	www.statsoft.com /textbook/glosr.html (4576 words)

	Logistic Equation -- from Wolfram MathWorld
		The logistic equation (sometimes called the Verhulst model or logistic growth curve) is a model of population growth first published by Pierre Verhulst (1845, 1847).
		The model is continuous in time, but a modification of the continuous equation to a discrete quadratic recurrence equation known as the logistic map is also widely used.
		The discrete version of the logistic equation (3) is known as the logistic map.
	mathworld.wolfram.com /LogisticEquation.html (240 words)

	Logistic Regression
		Logistic regression allows one to predict a discrete outcome, such as group membership, from a set of variables that may be continuous, discrete, dichotomous, or a mix of any of these.
		For example, logistic regression is often used in epidemiological studies where the result of the analysis is the probability of developing cancer after controlling for other associated risks.
		Logistic regression also provides knowledge of the relationships and strengths among the variables (e.g., smoking 10 packs a day puts you at a higher risk for developing cancer than working in an asbestos mine).
	userwww.sfsu.edu /~efc/classes/biol710/logistic/logisticreg.htm (1020 words)

	Logistic function Summary
		In addition, an important logistic function is the Rasch model, which is a general stochastic measurement model.
		logistic function and is often encountered in many technical domains, especially in artificial neural networks as a transfer function, probability, statistics, biomathematics, and economics.
		The logistic function is the inverse of the natural logit function and so can be used to convert the logarithm of odds into a probability; the conversion from the log-likelihood ratio of two alternatives also takes the form of a sigmoid curve.
	www.bookrags.com /Logistic_function (1196 words)

	Chapter 3 Logistic Regression Diagnostics
		When the assumptions of logistic regression analysis are not met, we may have problems, such as biased coefficient estimates or very large standard errors for the logistic regression coefficients, and these problems may lead to invalid statistical inferences.
		We assume that the logit function (in logistic regression) is the correct function to use.
		Since logistic regression uses the maximal likelihood principle, the goal in logistic regression is to minimize the sum of the deviance residuals.
	www.ats.ucla.edu /stat/stata/webbooks/logistic/chapter3/statalog3.htm (7550 words)

	Logistic function
		The terms logistic function and logistic curve mean either the standard sigmoid function, or any function obtained from it by linear scaling and translation; that is:
		These functions are found in a range of fields, from biology to economics.
		The logistic function is the inverse of the logit function and so can be used to convert the logarithm of odds into a probability; the conversion from the log-likelihood ratio of two alternatives also takes the form of a sigmoid curve.
	pedia.newsfilter.co.uk /wikipedia/l/lo/logistic_function.html (269 words)

	News \| Gainesville.com \| The Gainesville Sun \| Gainesville, Fla. (Site not responding. Last check: )
		Logistics is the management of resources and their distribution.
		The logistic function is a sigmoid function used in many fields.
		* Logit, the inverse of the logistic function, is fundamental to logistic regression.
	www.gainesville.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=logistic (125 words)

	Logistic function
		The sigmoid function or sigmoid curve is a special case of the logistic function (for parameters a = 1,m = 0,n = 1,τ = 1):
		This function is also called the standard logistic function and is often encountered in many technical domains, especially probability, statistics, biomathematics, and economics.
		In a neural network, a sigmoid function is often used to introduce nonlinearity in the model and/or to make sure that certain signals remains within a specified range.
	www.askfactmaster.com /Logistic_function (458 words)

	Subject: Analyzing the Spread of SARS with the Logistic Function
		Figure II Figure II is a plot of the derivative of the cumulative number of reported probable cases of Severe Acute Respiratory Syndrome, from March 17, 2003, to, April 22, 2003, the derivative of logistic function least-squares-best-fit to the data, and, the derivative of the exponential least-squares-best-fit to the data.
		Figure III is a plot of the fractional increase in the cumulative number of reported probable cases of Severe Acute Respiratory Syndrome, from March 17, 2003, to, April 22, 2003, the fractional increase of logistic function least-squares-best-fit to the data, and, the fractional increase of the exponential least-squares-best-fit to the data.
		Figure V is a plot of the cumulative number of reported probable cases of Severe Acute Respiratory Syndrome, from March 17, 2003, to, April 22, 2003, the logistic function least-squares-best-fit to the data, and the logistic function least-squares-best-fit to the data with its algorithmic convergence modified.
	www.johncon.com /john/correspondence/030423232715.15295.html (1175 words)

	The Logistic Distribution
		There are some who argue that the logistic distribution is inappropriate for modeling lifetime data because the left-hand limit of the distribution extends to negative infinity.
		One of the disadvantages of using the logistic distribution for reliability calculations is the fact that the logistic distribution starts at negative infinity.
		is the log-likelihood function of the normal distribution, described in the Statistical Background chapter and Appendix C.
	www.weibull.com /LifeDataWeb/the_logistic_distribution.htm (852 words)

	Bi-Logistic Growth - Perrin S. Meyer
		Although the logistic curve has often been criticized for being applied to systems where it is not appropriate, it has proved useful in modeling a wide range of phenomena.
		Thus, logistic growth can be viewed as a canonical form of growth for a system that is subject to forces that slow unconstrained growth.
		Curve C shows a growth process where a first pulse of logistic growth is joined by a second faster pulse, dubbed the "converging" logistic model, as the two pulses culminate about the same time.
	phe.rockefeller.edu /Bi-Logistic (3860 words)

	AES Abstract
		It is well known that these electrodes can cause local mass effect and reversible impairments in neurological function, however the effect of subdural electrodes on neurological function in the absence of clinically evident dysfunction is unknown.
		Subjects did a task that required them to detect an orientation change in a flashing visual stimulus that was presented either inside the mapped RF, or outside the RF in the diametrically opposite portion of the of the hemifield.
		Data were well fit by the logistic function in all four subjects for both RF and non-RF conditions.
	www.aesnet.org /Visitors/AnnualMeeting/Abstractsnew/dsp_Abstract.cfm?id=297 (341 words)

	4.2 Logistic Equation
		Many animal species are fertile only for a brief period during the year and the young are born in a particular season so that by the time they are ready to eat solid food it will be plentiful.
		The logistic equation is parabolic like the quadratic mapping with ƒ(0) = ƒ(1) = 0 and a maximum of ¼r at ½.
		There are two fixed points for this function: 0 and 1 − 1/r, the former being stable on the interval (−1, +1) and the latter on (1, 3).
	hypertextbook.com /chaos/42.shtml (897 words)

	Logistic Regression - Introduction
		Logistic regression estimates the probability of a certain event occurring.
		The values of this predictor variable are then transformed into probabilities by a logistic function.
		Such a function has the shape of an S. On the horizontal axis we have the values of the predictor variable, and on the vertical axis we have the probabilities.
	www.resample.com /xlminer/help/Lreg/lreg_intro.htm (307 words)

	Background
		The method generates either a linear discriminant function (the within-class covariance matrices are assumed to be equal) or a quadratic discriminant function (the within-class covariance matrices are assumed to be unequal).
		Press and Wilson (1978) compare logistic regression and parametric discriminant analysis and conclude that logistic regression is preferable to parametric discriminant analysis in cases for which the variables do not have multivariate normal distributions within classes.
		Efron (1975) shows that with two normal populations having a common covariance matrix, logistic regression is between one half and two thirds as effective as the linear discriminant function in achieving asymptotically the same error rate.
	www.uni.edu /sasdoc/stat/chap7/sect2.htm (682 words)

	Bifurcation
		These functions increased in complexity exponentially as the iteration number increased but by actually iterating we were able to produce graphs of these functions.
		In using the cursor to estimate the location of bifurcations in the logistic function attractor, remember that the precise location is marked by infinite iteration.
		The observation that the logistic function bifurcation cascades occur with such regularity was first publicized by a physicist named Mitchell Feigenbaum.
	www.mcasco.com /bifurcat.html (1159 words)

	Directory of open access journals
		The heart rate (HR) responses were evaluated by the mean index (mean ratio of all HR changes and mean arterial pressure (MAP) changes), by linear regression and by the logistic method (maximum gain of the sigmoid curve by a logistic function).
		The average gain evaluated by logistic function (-3.5 ± 0.6, -7.6 ± 1.3 and -3.8 ± 0.4 bpm/mmHg) was similar to the reflex tachycardic values, but different from the bradycardic values.
		Although two values of baroreflex sensitivity cannot be evaluated by a single symmetric logistic function, this method has the advantage of better comparing the baroreflex sensitivity of animals with different basal blood pressures.
	www.doaj.org /doaj?func=abstract&id=24523&recNo=18&toc=1 (361 words)

	Logistic Regression Notes
		Logistic regression implicitly uses prior probability estimates obtained from the sample.
		In discriminant analysis, a goal is to derive a function of the explanatory variables which is a classification index.
		An interesting alternative to logistic regression (indeed, to many problems) is that of "neural networks," which is in fact very similar to logistic regression.
	www.uic.edu /classes/idsc/ids470/jw4e/nts11_8.htm (1529 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		A logistic function or logistic curve models the S-curve of growth of some set P.
		This function is also called the standard logistic function and is often encountered in many technical domains, especially in artificial neural networks as a transfer function, probability, statistics, biomathematics, mathematical psychology and economics.
		Equation (2) is the continuous version of the logistic map.
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=Logistic_function (574 words)

	Logistic function - Education - Information - Educational Resources - Encyclopedia - Music
		The logistic function or logistic curve is defined by the mathematical formula:
		A typical application of the logistic equation is a common model of population growth states that:
		Beware that other functions with "S"-shaped graphs may also be called by this name: see sigmoid function.
	www.music.us /education/L/Logistic-function.htm (585 words)

	Logistic Innovations - What We Do
		Her outstanding record of success in client relations and operational procedures as well as proven ability in both external policy development and troubleshooting is evidenced by her ability to oversee the day-to-day operations of the business.
		Her expertise in process design and staff management facilitates the deployment of our support technology and best practices, ensuring that all employees are trained to maximize the efficiencies of the systems.
		Logistic Innovations will partner with you and work as an extension of your team to meet the objectives or your event.
	www.logisticinnovations.com /about/default.asp?sub=bios (831 words)

	Logistic function - meaning of word
		The logistic function or logistic curve models the #Sigmoid function of growth of some set P. The initial stage of growth is approximately exponential; then, as competition arises, the growth slows, and at maturity, growth stops.
		==The Verhulst equation== A typical application of the logistic equation is a common model of population growth, which states that: * the rate of reproduction is proportional to the existing population, all else being equal * the rate of reproduction is proportional to the amount of available resources, all else being equal.
		Verhulst derived his ''equation logistique'' (''logistic equation'') to describe the self-limiting growth of a biology population.
	www.wordsonline.org /Logistic_function (1076 words)

	Diagnosis method of alcholic or non-alcoholic steato-hepatitis using biochemical markers patent invention
		The method of claim 2, wherein said logistic function further comprises at least one biochemical marker chosen in the group constituted of alpha.2-macroglobulin, GGT (gammaglutamyl transpeptidase), total bilirubin, and haptoglobin.
		The method of claim 1, wherein said end value of the logistic function is further used for the diagnosis of alcoholic or non-alcoholic steato-hepatitis grade.
		d) instructions for using a logistic function that is used to combine said values in order to obtain an end value, wherein analysis of said end value determines the presence or absence of alcoholic or non-alcoholic steato-hepatitis in said patient.
	www.freshpatents.com /Diagnosis-method-of-alcholic-or-non-alcoholic-steato-hepatitis-using-biochemical-markers-dt20060803ptan20060172286.php?type=claims (657 words)

	Braz J Med Biol Res vol.32 no.3; Resumen: S0100-879X1999000300018 (Site not responding. Last check: )
		The heart rate (HR) responses were evaluated by the mean index (mean ratio of all HR changes and mean arterial pressure (MAP) changes), by linear regression and by the logistic method (maximum gain of the sigmoid curve by a logistic function).
		The average gain evaluated by logistic function (-3.5 ± 0.6, -7.6 ± 1.3 and -3.8 ± 0.4 bpm/mmHg) was similar to the reflex tachycardic values, but different from the bradycardic values.
		Although two values of baroreflex sensitivity cannot be evaluated by a single symmetric logistic function, this method has the advantage of better comparing the baroreflex sensitivity of animals with different basal blood pressures.
	www.scielo.br /scielo.php?script=sci_abstract&pid=S0100-879X1999000300018&lng=es&nrm=iso (360 words)

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