Indices and trends (TRIM)

Statistics Netherlands publishes national trends and indices based on monitoring data from the Network Ecological Monitoring (NEM). A specially developed program for analysing ecological data with many missing values was originally developed some 25 years ago by Statistics Netherlands (Pannekoek and Van Strien, 1991) and was made available as the freeware stand-alone program TRIM (TRends and Indices for Monitoring data). Although the program has had several updates since then, the original programming language has become outdated and requires further development. That is why TRIM was rebuilt as a package for the freely available and widely used open source statistical program R: RTRIM. RTRIM contains the same methods and models for nature monitoring data as the original versions of TRIM. It can still work with the same input data and produces exactly the same output data, but as a package in R it can easily be integrated in other R programming processes. New in this version is the in-built possibility to combine results from other TRIM runs, e.g. to combine results obtained from the analysis of regions of a country into a single new output with a combined trend, indices and standard errors. Being developed as R-package, TRIM is also made available for further development by the large R-society.
The renewed TRIM is available as RTRIM package on CRAN (Comprehensive R Archive Network)

Background TRIM method and indicators

Analysis of monitoring data with many missing values (PDF: 0,2MB)
Ter Braak et al., 1994

A loglinear poisson regression method to analyse bird monitoring data (PDF: 0,3MB)
A. van Strien et al. 2004

FAQ: frequently asked questions (Dutch site, English content)