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LambertW (version 0.6.9-1)

lp_norm: lp norm of a vector

Description

Computes the \(\ell^p\) norm of an n-dimensional (real/complex) vector \(\mathbf{x} \in \mathbf{C}^n\)

$$ \left|\left| \mathbf{x} \right|\right|_p = \left( \sum_{i=1}^n \left| x_i \right|^p \right)^{1/p}, p \in [0, \infty],$$

where \(\left| x_i \right|\) is the absolute value of \(x_i\). For \(p=2\) this is Euclidean norm; for \(p=1\) it is Manhattan norm. For \(p=0\) it is defined as the number of non-zero elements in \(\mathbf{x}\); for \(p = \infty\) it is the maximum of the absolute values of \(\mathbf{x}\).

The norm of \(\mathbf{x}\) equals \(0\) if and only if \(\mathbf{x} = \mathbf{0}\).

Usage

lp_norm(x, p = 2)

Value

Non-negative float, the norm of \(\mathbf{x}\).

Arguments

x

n-dimensional vector (possibly complex values)

p

which norm? Allowed values \(p \geq 0\) including Inf. Default: 2 (Euclidean norm).

Examples

Run this code

kRealVec <- c(3, 4)
# Pythagoras
lp_norm(kRealVec)
# did not know Manhattan,
lp_norm(kRealVec, p = 1)

# so he just imagined running in circles.
kComplexVec <- exp(1i * runif(20, -pi, pi))
plot(kComplexVec)
sapply(kComplexVec, lp_norm)

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