You are here

Random forests and stochastic gradient boosting for predicting tree canopy cover: Comparing tuning processes and model performance

Posted date: August 18, 2015
Publication Year: 
2014
Authors: Freeman, ElizabethMoisen, Gretchen; Coulston, J.; Wilson, B.
Publication Series: 
Abstract
Source: The International Forestry Review. 16(5): 408.

Abstract

Random forests (RF) and stochastic gradient boosting (SGB), both involving an ensemble of classification and regression trees, are compared for modeling tree canopy cover for the 2011 National Land Cover Database (NLCD). The objectives of this study were twofold. First, sensitivity of RF and SGB to choices in tuning parameters was explored. Second, performance of the two final models was compared by assessing the importance of, and interaction between, predictor variables, the global accuracy metrics derived from an independent test set, and the visual quality of the resultant maps of tree canopy cover. Examination of relative variable importance elucidated the differences in how RF and SGB make use of correlated predictor variables. SGB had a tendency to concentrate variable importance in fewer variables, whereas RF tended to spread importance out amongst more variables. The predictive accuracy of RF and SGB was remarkably similar on all four of the pilot regions, by all the accuracy measures examined. RF is simpler to implement than SGB, as RF both has fewer parameters needing tuning, and also was less sensitive to these parameters.

Citation

Freeman, E.; Moisen, G.; Coulston, J.; Wilson, B. 2014. Random forests and stochastic gradient boosting for predicting tree canopy cover: Comparing tuning processes and model performance. The International Forestry Review. 16(5): 408.