The Discriminant Value of Phase-Dependent Local Dynamic Stability of Daily Life Walking in Older Adult Community-Dwelling Fallers and Nonfallers

Figure 2

A schematic illustration of partial least square discriminant analysis (PLS-DA) and target projection (TP) used in the present study. The prediction matrix has a number of columns equal to the number of gait features and number of rows equal to the number of participants. The high number of gait features is projected to a small number of principle axes in the feature space and this projection is defined as the -scores (). The projection is provided by a weight matrix for the gait feature matrix and by a weight matrix for the categorical (faller and nonfaller) response variable . The target projection method combines the weight matrices and in order to define the influence of each gait feature in the discrimination between fallers and nonfallers. The cross-product of weights and is used to calculate the target projection scores , which is a variable containing one score for each older person which maximizes the discrimination between fallers and nonfallers. The target projection score is used to define the target projection loadings TP containing one loading for each gait feature that denotes its influence on the target projection score.