In complex analysis, given initial data consisting of n {\displaystyle n} points λ 1, …, λ n {\displaystyle \lambda _{1},\ldots,\lambda _{n}} in the complex unit disc D {\displaystyle \mathbb {D} } and target data consisting of n {\displaystyle n} points z 1, …, z n {\displaystyle z_{1},\ldots,z_{n}} in D {\displaystyle \mathbb {D} }, the Nevanlinna–Pick interpolation problem is to find a holomorphic function φ {\displaystyle \varphi } that interpolates the data, that is for all i ∈ { 1, . .. Wikipedia