Figure 1.

Geographic distribution and spatial variability of male lung cancer. The fill color in each ZIP code represents the SMR, with green indicating relatively low SMR and purple representing relatively high SMR (categories correspond to deciles of the histogram of rates). From these rates, a population-weighted semivariogram is computed in four directions. The semivariogram model (solid line) is used to filter the noise and short-range variability of observed SMR, yielding a smooth map of SMR local means (regional background).