Norm
Details and Options
- For complex numbers, Norm[z] is Abs[z].
- For vectors, Norm[v] is Sqrt[v.Conjugate[v]]. »
- For vectors, Norm[v,p] is Total[Abs[v]p](1/p).
- For vectors, Norm[v,Infinity] is the ‐norm given by Max[Abs[v]]. »
- For matrices, Norm[m] gives the maximum singular value of m. »
- Norm[m,"Frobenius"] gives the Frobenius norm of m. »
- Norm can be used on SparseArray objects. »
Examples
open allclose allScope (3)
Use exact arithmetic to compute the norm:
Use approximate machine-number arithmetic:
Use 35-digit precision arithmetic:
s is a SparseArray representation of v:
The norm is always real even when the input is complex:
TraditionalForm formatting:
Generalizations & Extensions (6)
Applications (3)
Estimate the mean distance from the origin to random points in the unit square:
Compare to the asymptotic result:
Solve an ill-conditioned linear system with a known solution:
Get the norm of the actual error:
Approximate the solution of using spatial points and time steps:
Find two solutions with fixed where the second has twice as many time steps:
Estimate the error by the norm of the difference:
Extrapolate to a better solution from the first-order convergence of the backward Euler method:
Compute a more accurate solution with NDSolve:
Properties & Relations (4)
The norm of v is equal to the square root of the Dot product :
The horizontal asymptote is the -norm, equal to Max[Abs[v]]:
The matrix 2-norm is the maximum 2-norm of m.v for all unit vectors v:
This is also equal to the largest singular value of :
The Frobenius norm is the same as the norm made up of the vector of the elements:
Possible Issues (2)
It is expensive to compute the 2-norm for large matrices:
If you need only an estimate, the 1-norm or -norm are very fast:
Norms of general vectors contain Abs:
Text
Wolfram Research (2003), Norm, Wolfram Language function, https://reference.wolfram.com/language/ref/Norm.html.
CMS
Wolfram Language. 2003. "Norm." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Norm.html.
APA
Wolfram Language. (2003). Norm. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Norm.html