Data analytics, statistics, and more
Left-censored environmental data are problematic because censored (nondetect) values are known only to range between zero and the detection or reporting limit. Fortunately, methods are available for analyzing data containing a mixture of detects and nondetects that make few or no assumptions about the data, or that substitute arbitrary values for the nondetects.
The Mahalanobis distance is a statistical technique that can be used to measure how distant a point is from the centroid of the data. Mahalanobis distances can be converted into probabilities using a chi-squared distribution. By specifying a significance level, this process is commonly used as an outlier detection method.
This post performs exploratory data analysis using time-series plots to visually identify essential economic information contained in the U.S. Bureau of Labor Statistics Employment Situation Report for February 2022.
This is a brief tutorial on using R and the trendMK package for the statistical analysis of groundwater monitoring data. The trendMK package is designed to analyze censored data sets containing many sampling locations and monitoring constituents.
Perform geospatial optimization of a groundwater monitoring well network with the objective of minimizing the number of sample locations needed to represent the plume, subject to the constraint that the characteristics of the plume remain comparable.
Use Sequential Gaussian Simulation (SGSIM) conditioned on measured groundwater concentration data to obtain quantitative measures of the uncertainty regarding the extent and severity of contamination at a site.
Costs for groundwater monitoring represent a significant, persistent, and growing burden for environmental remediation projects. This post examines spatial optimization of a groundwater monitoring well network using a geostatistic approach to identify new well locations or redundant locations such that the operational value of the monitoring network is maximized.
The Mann-Kendall test and Theil-Sen regression are typically used to detect temporal trend when analyzing environmental data. Both tests are affected by any value chosen to represent non-detects. Another method that is not affected by non-detects is Akritas-Theil-Sen nonparametric regression.
Conduct an evaluation of surface temperature change using temperature measurements that have been collected at Kremsmünster Abbey in Austria, which is considered to be one of the highest quality, longest running, instrumental temperature records in the world.
Landscapes contain complex spatial patterns in the distribution of resources that vary over time. This post examines the spatial analysis of landscapes using base R functions complemented by contributed packages for spatial pattern analysis and for quantifying landscape characteristics.