Cost matrix

A cost matrix is a matrix that is used to assess a classifier . It evaluates the various possibilities of a misclassification by costs . By multiplying the confusion matrix with a cost matrix, a Bayesian classifier can be set in such a way that the mean costs are the same and thus minimized.

example

For example, a manufacturer has to pay a fine if he does not label genetically modified food as such. In the opposite case, the costs result from the lost profit , since GMO-free food is a little more expensive to sell. The cost matrix in this case is ${\displaystyle L_{12}}$ ${\displaystyle L_{21}}$

${\displaystyle L={\begin{pmatrix}0&L_{12}\\L_{21}&0\end{pmatrix}}}$.