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| R2012a Documentation → Statistics Toolbox | |
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Classification margin
mar = margin(B,X,Y)
mar = margin(B,X,Y,'param1',val1,'param2',val2,...)
mar = margin(B,X,Y) computes the classification margins for predictors X given true response Y. The Y can be either a numeric vector, character matrix, cell array of strings, categorical vector or logical vector. mar is a numeric array of size Nobs-by-NTrees, where Nobs is the number of rows of X and Y, and NTrees is the number of trees in the ensemble B. For observation I and tree J, mar(I,J) is the difference between the score for the true class and the largest score for other classes. This method is available for classification ensembles only.
mar = margin(B,X,Y,'param1',val1,'param2',val2,...) specifies optional parameter name/value pairs:
| 'mode' | String indicating how the method computes errors. If set to 'cumulative' (default), margin computes cumulative errors and mar is an Nobs-by-NTrees matrix, where the first column gives error from trees(1), second column gives error fromtrees(1:2) etc, up to trees(1:NTrees). If set to 'individual', mar is a Nobs-by-NTrees matrix, where each element is an error from each tree in the ensemble. If set to 'ensemble', mar a single column of length Nobs showing the cumulative margins for the entire ensemble. |
| 'trees' | Vector of indices indicating what trees to include in this calculation. By default, this argument is set to 'all' and the method uses all trees. If 'trees' is a numeric vector, the method returns a vector of length NTrees for 'cumulative' and 'individual' modes, where NTrees is the number of elements in the input vector, and a scalar for 'ensemble' mode. For example, in the 'cumulative' mode, the first element gives error from trees(1), the second element gives error from trees(1:2) etc. |
| 'treeweights' | Vector of tree weights. This vector must have the same length as the 'trees' vector. The method uses these weights to combine output from the specified trees by taking a weighted average instead of the simple non-weighted majority vote. You cannot use this argument in the 'individual' mode. |
| 'useifort' | Logical matrix of size Nobs-by-NTrees indicating which trees should be used to make predictions for each observation. By default the method uses all trees for all observations. |
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