Classified and representative method - a useful way to select variables in ecology

In the study of biology and ecology, we always need to select variables for establishing the regression equation or for other statistical analysis. But a feature in some ecology problems is that there are too many variables related. This causes some difficulties. Suppose y is the function of x 1, x 2, ..., x m . The observation y i corresponds to x i1 , ..., x im ; 1 = 1, 2, ..., n. If n < m, some common statistical methods cannot be used. In our paper, we provide a new way, the classified and representative method, to select a set of variables from x 1, x 2, ..., x m for statistical analysis in the case of n < m.