Scheda di dettaglio – i prodotti della ricerca
| Dato | Valore |
|---|---|
| Title | Imputing censored data with desirable spatial covariance function properties using simulated annealing |
| Abstract | When measurements of values that are less than the limit of detection are reported as not detected, the data are referred to as censored. The non-recording of values below the limit of detection is common in soil science research although modelling data affected by censoring can be problematic. This paper develops and tests a modified version of Spatial Simulated Annealing, called Simulated Annealing by Variogram and Histogram form, for drawing values for censored points given a mixed set of observed and censored data. The algorithm aims to maximise the goodness of fitting between the experimental and theoretical variograms (by allowing variation in its parameters) while the imputed values are constrained to a target histogram form. In practice, the experimental histogram is estimated by transforming the available data (interval and exact observations) to quantiles and fitting a plausible distribution. The theoretical distribution of the data is used to constrain the variogram fitting. The proposed simulated annealing method is designed to find the optimal spatial arrangement of values, given by the lowest errors in variogram and histogram fitting and kriging prediction. The accuracy of the method proposed is assessed on a simulated data set in which the censored point values are known and compared with the Spatial Simulated Annealing algorithm. According to the results obtained, the Simulated Annealing by Variogram and Histogram form (SAVH) approach can be recommended as a useful tool for the analysis of spatially distributed data with censoring. |
| Source | Journal of geographical systems (Print) 14 (3), pp. 265–282 |
| Keywords | Detection limitAnnealing simulationVariogram and histogram fittingCross-validationKriging |
| Journal | Journal of geographical systems (Print) |
| Editor | Springer., Heidelberg, Germania |
| Year | 2010 |
| Type | Articolo in rivista |
| DOI | 10.1007/s10109-010-0145-1 |
| Authors | Sedda L., Atkinson P.M., Barca E.; Passarella G. |
| Text | 180439 2010 10.1007/s10109 010 0145 1 ISI Web of Science WOS 000305468900002 Scopus 2 s2.0 84862580497 Detection limit Annealing simulation Variogram and histogram fitting Cross validation Kriging Imputing censored data with desirable spatial covariance function properties using simulated annealing Sedda L., Atkinson P.M., Barca E.; Passarella G. L. Sedda Spatial Ecology and Epidemiology Group, University of Oxford, South Park Road, Oxford OX1 3PS, UK e mail luigi.sedda@zoo.ox.ac.uk P. M. Atkinson School of Geography, University of Southampton, Highfield, Southampton S017 1BJ, UK E. Barca, G. Passarella IRSA CNR, National Research Council, via F. De Blasio 5, 70123 Bari, Italy When measurements of values that are less than the limit of detection are reported as not detected, the data are referred to as censored. The non recording of values below the limit of detection is common in soil science research although modelling data affected by censoring can be problematic. This paper develops and tests a modified version of Spatial Simulated Annealing, called Simulated Annealing by Variogram and Histogram form, for drawing values for censored points given a mixed set of observed and censored data. The algorithm aims to maximise the goodness of fitting between the experimental and theoretical variograms by allowing variation in its parameters while the imputed values are constrained to a target histogram form. In practice, the experimental histogram is estimated by transforming the available data interval and exact observations to quantiles and fitting a plausible distribution. The theoretical distribution of the data is used to constrain the variogram fitting. The proposed simulated annealing method is designed to find the optimal spatial arrangement of values, given by the lowest errors in variogram and histogram fitting and kriging prediction. The accuracy of the method proposed is assessed on a simulated data set in which the censored point values are known and compared with the Spatial Simulated Annealing algorithm. According to the results obtained, the Simulated Annealing by Variogram and Histogram form SAVH approach can be recommended as a useful tool for the analysis of spatially distributed data with censoring. 14 http //link.springer.com/article/10.1007/s10109 010 0145 1 Articolo su rivista internazionale con IF Received 11 June 2010 / Accepted 25 November 2010 / Published online 12 December 2010 Imputing censored data with desirable spatial covariance function properties using simulated annealing Articolo su rivista internazionale con IF Received 11 June 2010 / Accepted 25 November 2010 / Published online 12 December 2010 INT_Articolo_in_Rivista_J_17.pdf Articolo in rivista Springer. 1435 5930 Journal of geographical systems Print Journal of geographical systems Print J. geogr. syst. Print Geographical systems Print. 1999 Print emanuele.barca BARCA EMANUELE giuseppe.passarella PASSARELLA GIUSEPPE TA.P04.005.008 Integrazione di metodologie per il monitoraggio e la modellizzazione per la gestione delle risorse idriche |