Figure 7From: Geostatistical analysis of disease data: estimation of cancer mortality risk from empirical frequencies using Poisson krigingDirectional semivariograms for breast and cervix cancer mortality rates with the anisotropic model fitted. The graphs for breast cancer (left column) were created by poisson_kriging.exe using the parameter file of Figure 3 with the option ndir = 4. The estimators are the followings: traditional semivariogram (Equation 8 with n(uα) = 1 ∀ α), population-weighted semivariogram (Equation 8), and risk semivariogram (Equation 18). The semivariograms are computed in four directions; azimuth angles are measured in degrees clockwise from the NS axis The solid curve denotes the anisotropic (i.e. direction-dependent) model fitted using weighted least-square regression.Back to article page