A Statistical Toolbox For Mining And Modeling Spatial Data

Most data mining projects in spatial economics start with an evaluation of a set of attribute variables on a sample of spatial entities, looking for the existence and strength of spatial autocorrelation, based on the Moran’s and the Geary’s coefficients, the adequacy of which is rarely challenged, despite the fact that when reporting on their properties, many users seem likely to make mistakes and to foster confusion. My paper begins by a critical appraisal of the classical definition and rational of these indices. I argue that while intuitively founded, they are plagued by an inconsistency in their conception. Then, I propose a principled small change leading to corrected spatial autocorrelation coefficients, which strongly simplifies their relationship, and opens the way to an augmented toolbox of statistical methods of dimension reduction and data visualization, also useful for modeling purposes. A second section presents a formal framework, adapted from recent work in statistical learning, which gives theoretical support to our definition of corrected spatial autocorrelation coefficients. More specifically, the multivariate data mining methods presented here, are easily implementable on the existing (free) software, yield methods useful to exploit the proposed corrections in spatial data analysis practice, and, from a mathematical point of view, whose asymptotic behavior, already studied in a series of papers by Belkin & Niyogi, suggests that they own qualities of robustness and a limited sensitivity to the Modifiable Areal Unit Problem (MAUP), valuable in exploratory spatial data analysis

High Risk of Anal and Rectal Cancer in Patients With Anal and/or Perianal Crohn’s Disease

International audienceBackground & AimsLittle is known about the magnitude of the risk of anal and rectal cancer in patients with anal and/or perineal Crohn’s disease. We aimed to assess the risk of anal and rectal cancer in patients with Crohn’s perianal disease followed up in the Cancers Et Surrisque Associé aux Maladies Inflammatoires Intestinales En France (CESAME) cohort.MethodsWe collected data from 19,486 patients with inflammatory bowel disease (IBD) enrolled in the observational CESAME study in France, from May 2004 through June 2005; 14.9% of participants had past or current anal and/or perianal Crohn’s disease. Subjects were followed up for a median time of 35 months (interquartile range, 29–40 mo). To identify risk factors for anal cancer in the total CESAME population, we performed a case-control study in which participants were matched for age and sex.ResultsAmong the total IBD population, 8 patients developed anal cancer and 14 patients developed rectal cancer. In the subgroup of 2911 patients with past or current anal and/or perianal Crohn’s lesions at cohort entry, 2 developed anal squamous-cell carcinoma, 3 developed perianal fistula–related adenocarcinoma, and 6 developed rectal cancer. The corresponding incidence rates were 0.26 per 1000 patient-years for anal squamous-cell carcinoma, 0.38 per 1000 patient-years for perianal fistula–related adenocarcinoma, and 0.77 per 1000 patient-years for rectal cancer. Among the 16,575 patients with ulcerative colitis or Crohn’s disease without anal or perianal lesions, the incidence rate of anal cancer was 0.08 per 1000 patient-years and of rectal cancer was 0.21 per 1000 patient-years. Among factors tested by univariate conditional regression (IBD subtype, disease duration, exposure to immune-suppressive therapy, presence of past or current anal and/or perianal lesions), the presence of past or current anal and/or perianal lesions at cohort entry was the only factor significantly associated with development of anal cancer (odds ratio, 11.2; 95% CI, 1.18-551.51; P = .03).ConclusionsIn an analysis of data from the CESAME cohort in France, patients with anal and/or perianal Crohn’s disease have a high risk of anal cancer, including perianal fistula–related cancer, and a high risk of rectal cancer