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In economics, the "J curve" is the time path of a country’s trade balance following a devaluation or depreciation of its currency, under a certain set of assumptions. A devalued currency means imports are more expensive, and on the assumption that the volumes of imports and exports change little at first, this causes a fall in the current ...
Exponential growth. Exponential growth occurs when the a quantity grows at a rate directly proportional to its present size. For example, when it is 3 times as big as it is now, it will be growing 3 times as fast as it is now. In more technical language, its instantaneous rate of change (that is, the derivative) of a quantity with respect to an ...
Logistic function. A logistic function or logistic curve is a common S-shaped curve (sigmoid curve) with the equation. where. is the carrying capacity, the supremum of the values of the function; is the logistic growth rate, the steepness of the curve; and. is the value of the function's midpoint.
A sigmoid function refers specifically to a function whose graph follows the logistic function. It is defined by the formula: In many fields, especially in the context of artificial neural networks, the term "sigmoid function" is correctly recognized as a synonym for the logistic function. While other S-shaped curves, such as the Gompertz curve ...
A Malthusian growth model, sometimes called a simple exponential growth model, is essentially exponential growth based on the idea of the function being proportional to the speed to which the function grows. The model is named after Thomas Robert Malthus, who wrote An Essay on the Principle of Population (1798), one of the earliest and most ...
The generalized logistic function or curve is an extension of the logistic or sigmoid functions. Originally developed for growth modelling, it allows for more flexible S-shaped curves. The function is sometimes named Richards's curve after F. J. Richards, who proposed the general form for the family of models in 1959.
If the graph starts above zero and drops a little before rising, it may be called a J curve. A hockey stick graph or hockey stick curve is a graph, or curve shape, that resembles an ice hockey stick, in that it turns sharply from a nearly flat "blade" to a long "handle". In economics, [1][2] marketing, [3] and dose–response relationships, [4 ...
Growth curve (biology) Figure 1: A bi-phasic bacterial growth curve. A growth curve is an empirical model of the evolution of a quantity over time. Growth curves are widely used in biology for quantities such as population size or biomass (in population ecology and demography, for population growth analysis), individual body height or biomass ...