WOLFRAM

gives the Kelvin function TemplateBox[{z}, KelvinKei].

KelvinKei[n,z]

gives the Kelvin function TemplateBox[{n, z}, KelvinKei2].

Details

  • Mathematical function, suitable for both symbolic and numerical manipulation.
  • For positive real values of parameters, TemplateBox[{n, z}, KelvinKei2]=Im(e^(-npii/2)TemplateBox[{n, {z, , {e, ^, {(, {pi, , {i, /, 4}}, )}}}}, BesselK]). For other values, is defined by analytic continuation.
  • KelvinKei[n,z] has a branch cut discontinuity in the complex z plane running from to .
  • KelvinKei[z] is equivalent to KelvinKei[0,z].
  • For certain special arguments, KelvinKei automatically evaluates to exact values.
  • KelvinKei can be evaluated to arbitrary numerical precision.
  • KelvinKei automatically threads over lists.

Examples

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Basic Examples  (6)Summary of the most common use cases

Evaluate numerically:

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Plot over a subset of the reals:

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Plot over a subset of the complexes:

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Series expansion at the origin:

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Series expansion at Infinity:

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Series expansion at a singular point:

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Scope  (34)Survey of the scope of standard use cases

Numerical Evaluation  (6)

Evaluate numerically:

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Evaluate to high precision:

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The precision of the output tracks the precision of the input:

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Complex number inputs:

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Evaluate efficiently at high precision:

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Compute average case statistical intervals using Around:

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Compute the elementwise values of an array:

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Or compute the matrix KelvinKei function using MatrixFunction:

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Specific Values  (3)

Values at zero:

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Find the first positive maximum of KelvinKei[0,x]:

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For some half-integer orders, KelvinKei evaluates to the same elementary functions:

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Visualization  (3)

Plot the KelvinKei function for integer () and half-integer () orders:

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Plot the real part of :

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Plot the imaginary part of :

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Plot the real part of :

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Plot the imaginary part of :

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Function Properties  (11)

The real domain of TemplateBox[{0, x}, KelvinKei2]:

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The complex domain of TemplateBox[{0, x}, KelvinKei2]:

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TemplateBox[{{-, {1, /, 2}}, x}, KelvinKei2] is defined for all real values greater than 0:

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The complex domain is the whole plane except :

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Approximate function range of TemplateBox[{0, x}, KelvinKei2]:

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Approximate function range of TemplateBox[{1, x}, KelvinKei2]:

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Recurrence relations:

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TemplateBox[{n, z}, KelvinKei2] is not an analytic function:

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KelvinKei is neither non-decreasing nor non-increasing:

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KelvinKei is not injective:

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KelvinKei is neither non-negative nor non-positive:

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KelvinKei has both singularity and discontinuity for z0:

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KelvinKei is neither convex nor concave:

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TraditionalForm formatting:

Differentiation  (3)

The first derivative with respect to z:

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The first derivative with respect to z when n=1:

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Higher derivatives with respect to z:

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Plot the higher derivatives with respect to z:

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Formula for the ^(th) derivative with respect to z:

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Integration  (3)

Compute the indefinite integral using Integrate:

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Verify the anti-derivative:

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The definite integral:

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More integrals:

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Series Expansions  (5)

Find the Taylor expansion using Series:

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Plots of the first three approximations around :

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The general term in the series expansion using SeriesCoefficient:

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Find the series expansion at Infinity:

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Find the series expansion for an arbitrary symbolic direction :

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The Taylor expansion at a generic point:

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Generalizations & Extensions  (1)Generalized and extended use cases

KelvinKei can be applied to a power series:

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Applications  (3)Sample problems that can be solved with this function

Solve the Kelvin differential equation:

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Plot the radial density profile for alternating current within a hollow cylinder:

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For some values, expressions with MeijerG are represented with KelvinKei:

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Properties & Relations  (4)Properties of the function, and connections to other functions

Use FullSimplify to simplify expressions involving Kelvin functions:

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Use FunctionExpand to expand Kelvin functions of half-integer orders:

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Integrate expressions involving Kelvin functions:

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KelvinKei can be represented in terms of MeijerG:

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Possible Issues  (1)Common pitfalls and unexpected behavior

The oneargument form evaluates to the two-argument form:

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Wolfram Research (2007), KelvinKei, Wolfram Language function, https://reference.wolfram.com/language/ref/KelvinKei.html.
Wolfram Research (2007), KelvinKei, Wolfram Language function, https://reference.wolfram.com/language/ref/KelvinKei.html.

Text

Wolfram Research (2007), KelvinKei, Wolfram Language function, https://reference.wolfram.com/language/ref/KelvinKei.html.

Wolfram Research (2007), KelvinKei, Wolfram Language function, https://reference.wolfram.com/language/ref/KelvinKei.html.

CMS

Wolfram Language. 2007. "KelvinKei." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/KelvinKei.html.

Wolfram Language. 2007. "KelvinKei." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/KelvinKei.html.

APA

Wolfram Language. (2007). KelvinKei. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/KelvinKei.html

Wolfram Language. (2007). KelvinKei. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/KelvinKei.html

BibTeX

@misc{reference.wolfram_2025_kelvinkei, author="Wolfram Research", title="{KelvinKei}", year="2007", howpublished="\url{https://reference.wolfram.com/language/ref/KelvinKei.html}", note=[Accessed: 29-March-2025 ]}

@misc{reference.wolfram_2025_kelvinkei, author="Wolfram Research", title="{KelvinKei}", year="2007", howpublished="\url{https://reference.wolfram.com/language/ref/KelvinKei.html}", note=[Accessed: 29-March-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_kelvinkei, organization={Wolfram Research}, title={KelvinKei}, year={2007}, url={https://reference.wolfram.com/language/ref/KelvinKei.html}, note=[Accessed: 29-March-2025 ]}

@online{reference.wolfram_2025_kelvinkei, organization={Wolfram Research}, title={KelvinKei}, year={2007}, url={https://reference.wolfram.com/language/ref/KelvinKei.html}, note=[Accessed: 29-March-2025 ]}