Dendrochronologia 30 (2012) 57–60 Contents lists available at ScienceDirect Dendrochronologia journal homepage: www.elsevier.de/dendro Technical note detrendeR – A Graphical User Interface to process and visualize tree-ring data using R Filipe Campelo a,* , Ignacio García-González b , Cristina Nabais a a Centro de Ecologia Funcional, Departamento de Ciências da Vida, Universidade de Coimbra, 3001-401 Coimbra, Portugal b Departamento de Botánica, Escola Politécnica Superior, Universidade de Santiago de Compostela, Campus de Lugo, 27002 Lugo, Spain article info Article history: Received 16 September 2010 Accepted 19 January 2011 Keywords: ARSTAN Chronology Detrending GUI R language abstract In this paper, we present the package detrendeR, a Graphical User Interface to facilitate the visualization and analysis of dendrochronological data, using the R computing environment. This package offers an easy way to perform most of the traditional tasks in dendrochronology: detrending, chronology building and graphical presentation of time series. The advantage of detrendeR, compared with the program ARSTAN, is the graphical interface that provides the user with an easy way to use R language, rich in graphics and handling routines, with no need to type commands. The detrendeR uses a simple and familiar dialog- box interface and it can read Tucson decadal-format files (*.rwl and *.crn) as well as plain text files. In addition, detrendeR has the ability to test temporal changes of the common signal using moving intervals. The detrendeR should make it easier to perform detrending and chronology building of tree-ring series, taking advantage of the R statistical programming environment. © 2011 Istituto Italiano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved. Introduction Chronology building and quality assessment are two of the most important tasks in dendrochronological research. For many years dendrochronologists have been using ARSTAN, which produces chronologies from tree-ring series after detrending, and computes tree-ring indices (Cook, 1985). An autoregressive model can also be applied either to the index series before averaging all of them, or to the final chronology, if still showing persistence, and chronol- ogy quality is assessed on a common interval including most of the series. Though very powerful, ARSTAN runs in a Command Line Interface (CLI), which poses some difficulties to new users. Chronol- ogy building and quality assessment can also be carried out by other command line environments such as Matlab (Meko, 2002) and more recently by R, with the introduction of recent packages such as dplR (Bunn, 2008; Bunn, 2010) and bootRes (Zang, 2009). R is an interpreted programming language with a run-time environ- ment with graphics, a debugger, access to certain system functions and the ability to run commands stored in script files, allowing the user to create specific functions and routines to solve their own problems, being therefore easily extensible (R Development Core Team, 2009). Moreover, R is open source and thus available under the GNU license agreement. Several hundred packages are avail- able on CRAN and other sites for free download to R users and even * Corresponding author. E-mail address: fcampelo@ci.uc.pt (F. Campelo). new statistical methods are often first “published” as R packages before being adapted to commercial statistical software. R uses a CLI meaning that commands should be entered into the R console window to perform specific tasks. This is the preferred interface for experienced users, with a good knowledge of the R language, because it allows direct control on calculations and it is flexible. For introductory, educational and sporadic use of the R language, a Graphical User Interface (GUI) is particularly attractive. GUIs allow the user to interact with the computer in more ways than typing, and therefore the learning time is typically shorter as the user does not need to remember commands, also decreasing the syntax and typing errors. In fact, the R language has already some GUIs, like the Rcmdr (Fox, 2005) and de ade4TkGUI (Thioulouse and Dray, 2009) packages. The main purpose of this paper is to introduce a new tool called detrendeR, which combines GUI with R. This tool uses the most required statistical tools for detrending tree-ring width series, as well as chronology building and characterization. The main win- dow of the program supplies a group of menus, buttons, and dialog boxes to read, manipulate, analyze and visualize data, without the need to type any command into the R console window. In addi- tion, users with strong knowledge of R language can also type R commands directly in the R console in association with detrendeR. detrendeR To correctly work under Windows, the detrendeR GUI requires the single-document interface (SDI) to R, so that the detrendeR and 1125-7865/$ – see front matter © 2011 Istituto Italiano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.dendro.2011.01.010