Kronecker delta

Definition

δ(k−k0)=δkk0={0for k≠k01for k=k0\delta(k-k_0) = \delta_{kk_0} = \begin{cases} 0 \quad \text{for } k \neq k_0 \\ 1 \quad \text{for } k = k_0 \end{cases}

Applications

Sifting property:

See also: Discrete step function