Symmetric mean absolute percentage error

The symmetric mean absolute percentage error (SMAPE or sMAPE) is an accuracy measure based on percentage (or relative) errors. It is usually defined as follows: SMAPE = 2 n ∑ t = 1 n | F t − A t | | A t | + | F t | {\displaystyle {\text{SMAPE}}={\frac {2}{n}}\sum _{t=1}^{n}{\frac {\left|F_{t}-A_{t}\right|}{|A_{t}|+|F_{t}|}}} where A t {\displaystyle A_{t}} are the actual values and F t {\displaystyle F_{t}} are the forecasted values.

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