# LAMBDA

**What is LAMBDA?**

LAMBDA is a MatLab toolkit designed to do MAR-1 based data analysis on long-term datasets (i.e., time series). LAMBDA is designed to allow the user to step through the entire modeling process, from importing the data into a format readable by MatLab, to re-scaling the data as necessary, to obtaining descriptive statistics of the dataset, to, finally, performing a MAR-1 regression model and obtaining output parameters (see Ives et al. 2003, Ecological Monographs 73:301-330). A MAR-1 process is a Multivariate, Auto-Regressive first (1st) order process. Essentially, it is a means of estimating interactions between multiple variates from time series data, using matrix algebra. A MAR-1 model is a stochastic, non-mechanistic model that uses time series data to deduce inter-population interactions, and the effects of covariates (e.g., physical variables) on populations. Normally, the data exist in a time series for each species or population, and the only things known are the population sizes, such as data obtained by population censues, or from fishery landing data. If the time series is of sufficient length ("sufficient" being determined from the nature of the data), the strength and direction of interactions between all species and the measured environmental covariates can be estimated in a manner similar to a multivariate regression.

**What is the target audience of LAMBDA?**

LAMBDA's target audience is professional scientists and managers who have long-term ecological data (information on counts or biomass of organisms per unit area). LAMBDA is designed to work with field data, of the sort one would have from surveys taken in the same area over many months or years, although just about any data in a time series can be used with it.

**Where does it come from?**

LAMBDA is a product of the Mathematical Biology program at the Northwest Fisheries Science Center (NWFSC) in Seattle, WA. NWFSC is the NW regional research center for the National Marine Fisheries Service (NMFS) which is part of the National Oceanic Atmospheric Administration (NOAA). LAMBDA was developed with support by NOAA/NMFS and the National Research Council. It is open-source software released under the GNU GPL license, meaning you are free to use and modify it in (almost) any non-commercial way you see fit. You can find out more about the licensing here. . LAMBDA was developed by Steven Viscido while on a National Research Council postdoctoral associateship with Dr. Elizabeth Holmes (at NWFSC).

**Credits**

LAMBDA is based on the techniques outlined in the paper, Ives et al. 2003, Ecological Monographs 73:301-330. The code for the actual MAR-1 regression was based on the "MARbasic.m" MatLab script written by Tony Ives (available at the Ecological Archives). The parameter search code was based on an unpublished script written by Tony Ives. All other code was written by Steven Viscido.

**License**

LAMBDA is an open-source software package that is licensed under the GNU General Public License. Read license here. Please note the disclaimer of warranty before downloading and installing.

From the GNU General Public License: "11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION."

## No comments