CauchyMatrix
✖
CauchyMatrix

represents the Cauchy matrix given by the generating vectors x and y as a structured array.
Details and Options


- Cauchy matrices, when represented as structured arrays, allow for efficient storage and more efficient operations, including Det, Inverse and LinearSolve.
- Cauchy matrices occur in computations related to rational interpolation, conformal mappings, n-body simulations and the discretization of integral equations with singular kernels.
- Given generating vectors x and y, the resulting Cauchy matrix
has entries given by
.
- Operations that are accelerated for CauchyMatrix include:
-
Det time Inverse time LinearSolve time - For a CauchyMatrix sa, the following properties "prop" can be accessed as sa["prop"]:
-
"XVector" generating vector x "YVector" generating vector y "Properties" list of supported properties "Structure" type of structured array "StructuredData" internal data stored by the structured array "StructuredAlgorithms" list of functions with special methods for the structured array "Summary" summary information, represented as a Dataset - Normal[CauchyMatrix[x]] gives the Cauchy matrix as an ordinary matrix.
- CauchyMatrix[…,TargetStructure->struct] returns the Cauchy matrix in the format specified by struct. Possible settings include:
-
Automatic automatically choose the representation returned "Dense" represent the matrix as a dense matrix "Structured" represent the matrix as a structured array "Symmetric" represent the matrix as a symmetric matrix - CauchyMatrix[…,TargetStructureAutomatic] is equivalent to CauchyMatrix[…,TargetStructure"Structured"].

Examples
open allclose allBasic Examples (2)Summary of the most common use cases

https://wolfram.com/xid/0mk6sixnr58y-c8lcdu


https://wolfram.com/xid/0mk6sixnr58y-eeqd95

Normal can convert a CauchyMatrix to its ordinary representation:

https://wolfram.com/xid/0mk6sixnr58y-n70yk

Construct a Cauchy matrix with symbolic entries:

https://wolfram.com/xid/0mk6sixnr58y-n8t2ck


https://wolfram.com/xid/0mk6sixnr58y-cbmlaq


https://wolfram.com/xid/0mk6sixnr58y-eqlw3y

Scope (6)Survey of the scope of standard use cases
Generate a symmetric Cauchy matrix:

https://wolfram.com/xid/0mk6sixnr58y-hxwq2h


https://wolfram.com/xid/0mk6sixnr58y-e57tdh

Get the normal representation:

https://wolfram.com/xid/0mk6sixnr58y-qmwi51

Generate a rectangular Cauchy matrix:

https://wolfram.com/xid/0mk6sixnr58y-e90wt0


https://wolfram.com/xid/0mk6sixnr58y-erdlat

Get the normal representation:

https://wolfram.com/xid/0mk6sixnr58y-noq6o

Represent a dense Cauchy matrix as a structured array:

https://wolfram.com/xid/0mk6sixnr58y-6ir4q


https://wolfram.com/xid/0mk6sixnr58y-ktayaj

The structured representation typically uses much less memory:

https://wolfram.com/xid/0mk6sixnr58y-e0dv3v


https://wolfram.com/xid/0mk6sixnr58y-jvuy24

CauchyMatrix objects include properties that give information about the array:

https://wolfram.com/xid/0mk6sixnr58y-b621dk


https://wolfram.com/xid/0mk6sixnr58y-llpipt

The "XVector" and "YVector" properties give the generating vectors of the Cauchy matrix:

https://wolfram.com/xid/0mk6sixnr58y-b3ncvr


https://wolfram.com/xid/0mk6sixnr58y-e266ys

The "Summary" property gives a brief summary of information about the array:

https://wolfram.com/xid/0mk6sixnr58y-ut0aor

The "StructuredAlgorithms" property lists the functions that have structured algorithms:

https://wolfram.com/xid/0mk6sixnr58y-33g6sl

When appropriate, structured algorithms return another CauchyMatrix object:

https://wolfram.com/xid/0mk6sixnr58y-otpl4i

The transpose is also a CauchyMatrix:

https://wolfram.com/xid/0mk6sixnr58y-471hf

The product of a Cauchy matrix and its transpose is no longer a Cauchy matrix:

https://wolfram.com/xid/0mk6sixnr58y-dn5lzg

Options (1)Common values & functionality for each option
TargetStructure (1)
Return the Cauchy matrix as a dense matrix:

https://wolfram.com/xid/0mk6sixnr58y-e3t5fj

Return the Cauchy matrix as a structured array:

https://wolfram.com/xid/0mk6sixnr58y-numczz

Return the Cauchy matrix as a symmetric matrix:

https://wolfram.com/xid/0mk6sixnr58y-db5mic

Applications (3)Sample problems that can be solved with this function
Represent the Hilbert matrix as a CauchyMatrix:

https://wolfram.com/xid/0mk6sixnr58y-844dq
Compare with HilbertMatrix:

https://wolfram.com/xid/0mk6sixnr58y-heqss

Numerically compute the inverse for a large Hilbert matrix:

https://wolfram.com/xid/0mk6sixnr58y-uu8jb


The result from the structured version is more accurate:

https://wolfram.com/xid/0mk6sixnr58y-el3pv1

Use CauchyMatrix to compute the coefficients for an interpolating rational function with fixed poles:

https://wolfram.com/xid/0mk6sixnr58y-c48q3t

Construct the rational function:

https://wolfram.com/xid/0mk6sixnr58y-c01m3e

Visualize the interpolant in the complex plane:

https://wolfram.com/xid/0mk6sixnr58y-m4n9uq

Check that the rational interpolant does pass through all the given points:

https://wolfram.com/xid/0mk6sixnr58y-frjr1z

Define the Parter matrix as a CauchyMatrix:

https://wolfram.com/xid/0mk6sixnr58y-dfvxma
The Parter matrix is both a Cauchy matrix and a Toeplitz matrix:

https://wolfram.com/xid/0mk6sixnr58y-l7mqi6


https://wolfram.com/xid/0mk6sixnr58y-dtzwbr

The Parter matrix's dominant singular values are clustered around :

https://wolfram.com/xid/0mk6sixnr58y-hg92fe


https://wolfram.com/xid/0mk6sixnr58y-eotdp

Properties & Relations (2)Properties of the function, and connections to other functions
Express a Cauchy matrix as a product of diagonal matrices, Vandermonde matrices and their inverses:

https://wolfram.com/xid/0mk6sixnr58y-b8vepm

Express a Cauchy matrix as a product of diagonal, Vandermonde and Hankel matrices:

https://wolfram.com/xid/0mk6sixnr58y-fymf5y

Possible Issues (3)Common pitfalls and unexpected behavior
The literature sometimes uses a different definition of the Cauchy matrix, where the second generating vector is negated:

https://wolfram.com/xid/0mk6sixnr58y-bz1i88

If any of the generating vectors have repeated entries, a Cauchy matrix cannot be constructed:

https://wolfram.com/xid/0mk6sixnr58y-e3bwaw


If a component of any one of the generating vectors is the negative of a component of the other generating vector, a Cauchy matrix cannot be constructed:

https://wolfram.com/xid/0mk6sixnr58y-bpafh


Wolfram Research (2022), CauchyMatrix, Wolfram Language function, https://reference.wolfram.com/language/ref/CauchyMatrix.html (updated 2024).
Text
Wolfram Research (2022), CauchyMatrix, Wolfram Language function, https://reference.wolfram.com/language/ref/CauchyMatrix.html (updated 2024).
Wolfram Research (2022), CauchyMatrix, Wolfram Language function, https://reference.wolfram.com/language/ref/CauchyMatrix.html (updated 2024).
CMS
Wolfram Language. 2022. "CauchyMatrix." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2024. https://reference.wolfram.com/language/ref/CauchyMatrix.html.
Wolfram Language. 2022. "CauchyMatrix." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2024. https://reference.wolfram.com/language/ref/CauchyMatrix.html.
APA
Wolfram Language. (2022). CauchyMatrix. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/CauchyMatrix.html
Wolfram Language. (2022). CauchyMatrix. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/CauchyMatrix.html
BibTeX
@misc{reference.wolfram_2025_cauchymatrix, author="Wolfram Research", title="{CauchyMatrix}", year="2024", howpublished="\url{https://reference.wolfram.com/language/ref/CauchyMatrix.html}", note=[Accessed: 24-April-2025
]}
BibLaTeX
@online{reference.wolfram_2025_cauchymatrix, organization={Wolfram Research}, title={CauchyMatrix}, year={2024}, url={https://reference.wolfram.com/language/ref/CauchyMatrix.html}, note=[Accessed: 24-April-2025
]}