An Approximation Algorithm for l_infinity Fitting Robinson Structures to Distances

In this paper, we present a factor 16 approximation algorithm for the following NP-hard distance fitting problem: given a finite set $X$ and a distance $d$ on $X$, find a Robinsonian distance $d_R$ on $X$ minimizing the $l_{infty}$-error $||d-d_R||_{infty}=mbox{max}_{x,yin X}{ |d(x,y)-d_R(x,y)|}.$ A distance $d_R$ on a finite set $X$ is Robinsonian if its matrix can be symmetrically permuted so that its elements do not decrease when moving away from the main diagonalalong any row or column. Robinsonian distances generalize ultrametrics, line distances and occur in the seriation problems and in classification