KroneckerDelta [n1,n2,…]
gives the Kronecker delta , equal to 1 if all the are equal, and 0 otherwise.
KroneckerDelta
KroneckerDelta [n1,n2,…]
gives the Kronecker delta , equal to 1 if all the are equal, and 0 otherwise.
Details
- KroneckerDelta [0] gives 1; KroneckerDelta [n] gives 0 for other numeric n.
- KroneckerDelta has attribute Orderless .
- An empty template can be entered as kd. Arguments in the subscript should be separated by commas.
- The comma can be made invisible by using the character \[InvisibleComma] or ,.
- KroneckerDelta automatically threads over lists. »
Examples
open all close allBasic Examples (4)
Evaluate numerically:
Construct an identity matrix:
Use in sums to pick out elements:
Plot over a subset of the integers:
Scope (26)
Numerical Evaluation (6)
Evaluate numerically:
Complex number inputs:
KroneckerDelta always returns an exact result irrespective of the precision of the input:
Evaluate efficiently at high precision:
Compute the elementwise values of an array using automatic threading:
Or compute the matrix KroneckerDelta function using MatrixFunction :
Compute average-case statistical intervals using Around :
Specific Values (3)
Value at zero:
The multi-argument form gives 1 when all inputs are equal:
Evaluate symbolically:
Visualization (3)
Plot the single-argument KroneckerDelta using integer-width bins:
Visualize KroneckerDelta over the reals. Except for a jump at , it is indistinguishable from a zero function:
Plot KroneckerDelta in three dimensions:
Function Properties (10)
KroneckerDelta is defined for all real and complex inputs:
Function range of KroneckerDelta :
The function range for complex values is the same:
KroneckerDelta accepts list inputs:
The traditional notation is used in both StandardForm and TraditionalForm :
KroneckerDelta is not an analytic function:
It has both singularities and discontinuities:
KroneckerDelta is neither nondecreasing nor nonincreasing:
KroneckerDelta is not injective:
KroneckerDelta is not surjective:
KroneckerDelta is non-negative:
KroneckerDelta is neither convex nor concave:
Differentiation and Integration (4)
First derivative with respect to :
Series expansion at a generic point:
Compute the indefinite integral using Integrate :
Verify the antiderivative:
More integrals:
Applications (5)
Use in sums to pick out terms:
Generate a banded matrix with two superdiagonals:
Pick out elements:
Compute MoebiusMu using KroneckerDelta and LiouvilleLambda :
Decompose a spherical harmonic into a sum of products of two spherical harmonics:
Properties & Relations (2)
Reduce an equation containing KroneckerDelta :
The support of KroneckerDelta has measure zero:
Possible Issues (2)
KroneckerDelta can stay unevaluated for numeric arguments:
A larger setting for $MaxExtraPrecision can be needed:
Equality testing of the arguments takes numerical precision into account:
Neat Examples (1)
Express products of signatures as sums of products of Kronecker deltas:
Special cases for 3D; summation over repeated indices is assumed:
Tech Notes
Related Guides
Related Links
History
Introduced in 1999 (4.0) | Updated in 2017 (11.1)
Text
Wolfram Research (1999), KroneckerDelta, Wolfram Language function, https://reference.wolfram.com/language/ref/KroneckerDelta.html (updated 2017).
CMS
Wolfram Language. 1999. "KroneckerDelta." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2017. https://reference.wolfram.com/language/ref/KroneckerDelta.html.
APA
Wolfram Language. (1999). KroneckerDelta. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/KroneckerDelta.html
BibTeX
@misc{reference.wolfram_2025_kroneckerdelta, author="Wolfram Research", title="{KroneckerDelta}", year="2017", howpublished="\url{https://reference.wolfram.com/language/ref/KroneckerDelta.html}", note=[Accessed: 04-January-2026]}
BibLaTeX
@online{reference.wolfram_2025_kroneckerdelta, organization={Wolfram Research}, title={KroneckerDelta}, year={2017}, url={https://reference.wolfram.com/language/ref/KroneckerDelta.html}, note=[Accessed: 04-January-2026]}