ramp function - wikipedia, the free encyclopedia
TRANSCRIPT
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11/15/11 Ramp function - Wikipedia, the free encyclopedia
1/3en.wikipedia.org/wiki/Ramp_function
Graph of the ramp function
Ramp functionFrom Wikipedia, the free encyclopedia
The ramp function is an elementary unary real function, easily computable as the mean of its independent variableand its absolute value.
This function is applied in engineering (e.g., in the theory of DSP). The name ramp function can be derived by thelook of its graph.
Contents
1 Definitions
2 Analytic properties
2.1 Non-negativity
2.2 Derivative
2.3 Fourier transform
2.4 Laplace transform
3 Algebraic properties3.1 Iteration invariance
4 References
Definitions
The ramp function ( ) may be defined
analytically in several ways. Possible definitions are:
The mean of a straight line with unity gradient and its
modulus:
this can be derived by noting the following definition of ,
for which a = x and b = 0
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11/15/11 Ramp function - Wikipedia, the free encyclopedia
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The Heaviside step function multiplied by a straight line with unity gradient:
The convolution of the Heaviside step function with itself:
The integral of the Heaviside step function:
Analytic properties
Non-negativity
In the whole domain the function is non-negative, so its absolute value is itself, i.e.
and
Proof: by the mean of definition [2] it is non-negative in the I. quarter, and zero in the II.; so everywhere
it is non-negative.
Derivative
Its derivative is the Heaviside function:
From this property definition [5]. goes.
Fourier transform
= =
Where δ ( x ) is the Dirac delta (in this formula, its derivative appears).
Laplace transform
The single-sided Laplace transform of R(x) is given as follows,
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11/15/11 Ramp function - Wikipedia, the free encyclopedia
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Algebraic properties
Iteration invariance
Every iterated function of the ramp mapping is itself, as
.
Proof: =
= .
We applied the non-negative property.
References
Mathworld (http://mathworld.wolfram.com/RampFunction.html)
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Categories: Mathematical analysis Elementary special functions
This page was last modified on 21 October 2011 at 20:40.
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