# meanMargin

Mean classification margin

## Syntax

`mar = meanMargin(B,TBLnew,Ynew)`

mar = meanMargin(B,Xnew,Ynew)

mar = meanMargin(B,TBLnew,Ynew,'param1',val1,'param2',val2,...)

mar
= meanMargin(B,Xnew,Ynew,'param1',val1,'param2',val2,...)

## Description

`mar = meanMargin(B,TBLnew,Ynew)`

computes average classification
margins for the predictors contained in the table `TBLnew`

given the true
response `Ynew`

. You can omit `Ynew`

if
`TBLnew`

contains the response variable. If you trained
`B`

using sample data contained in a table, then the input data for this
method must also be in a table.

`mar = meanMargin(B,Xnew,Ynew)`

computes average classification margins
for the predictors contained in the matrix `Xnew`

given true response
`Ynew`

. If you trained `B`

using sample data contained in
a matrix, then the input data for this method must also be in a matrix.

`Ynew`

can be a numeric vector, character matrix, string array, cell
array of character vectors, categorical vector, or logical vector.
`meanMargin`

averages the margins over all observations (rows) in
`TBLnew`

or `Xnew`

for each tree. `mar`

is a matrix of size 1-by-`NTrees`

, where `NTrees`

is the
number of trees in the ensemble `B`

. This method is available for
classification ensembles only.

`mar = meanMargin(B,TBLnew,Ynew,'param1',val1,'param2',val2,...)`

or
```
mar
= meanMargin(B,Xnew,Ynew,'param1',val1,'param2',val2,...)
```

specifies
optional parameter name-value pairs:

`'Mode'` | How `meanMargin` computes errors. If set to
`'cumulative'` (default), is a vector of length
`NTrees` where the first element gives mean margin from
`trees(1)` , second column gives mean margins from
`trees(1:2)` etc., up to `trees(1:NTrees)` . If
set to `'individual'` , `mar` is a vector of length
`NTrees` , where each element is a mean margin from each tree in
the ensemble . If set to `'ensemble'` , `mar` is a
scalar showing the cumulative mean margin 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 mean margin from
`trees(1)` , the second element gives mean margin from
`trees(1:2)` etc. |

`'TreeWeights'` | Vector of tree weights. This vector must have the same length as the
`'Trees'` vector. `meanMargin` uses these
weights to combine output from the specified trees by taking a weighted average
instead of the simple nonweighted majority vote. You cannot use this argument in the
`'individual'` mode. |

`'UseInstanceForTree'` | Logical matrix of size `Nobs` -by-`NTrees`
indicating which trees to use to make predictions for each observation. By default,
the method uses all trees for all observations. |

`'Weights'` | Vector of observation weights to use for margin averaging. By default, the weight of each observation is set to 1. The length of this vector must be equal to the number of rows in X. |