# accuracy module

The `surprise.accuracy` module provides tools for computing accuracy metrics on a set of predictions.

Available accuracy metrics:

`rmse` | Compute RMSE (Root Mean Squared Error).
`mse` | Compute MSE (Mean Squared Error).
`mae` | Compute MAE (Mean Absolute Error).
`fcp` | Compute FCP (Fraction of Concordant Pairs).

`surprise.accuracy.``fcp`(predictions, verbose=True)

  Compute FCP (Fraction of Concordant Pairs).

  Computed as described in paper Collaborative Filtering on Ordinal User Feedback by Koren and Sill, section 5.2.

  Parameters: | predictions (`list` of `Prediction`) – A list of predictions, as returned by the `test()` method. verbose – If True, will print computed value. Default is `True`.
  Returns: | The Fraction of Concordant Pairs.
  Raises: | `ValueError` – When `predictions` is empty.

`surprise.accuracy.``mae`(predictions, verbose=True)

  Compute MAE (Mean Absolute Error).

  \[\text{MAE} = \frac{1}{|\hat{R}|} \sum_{\hat{r}_{ui} \in \hat{R}}|r_{ui} - \hat{r}_{ui}|\]

  Parameters: | predictions (`list` of `Prediction`) – A list of predictions, as returned by the `test()` method. verbose – If True, will print computed value. Default is `True`.
  Returns: | The Mean Absolute Error of predictions.
  Raises: | `ValueError` – When `predictions` is empty.

`surprise.accuracy.``mse`(predictions, verbose=True)

  Compute MSE (Mean Squared Error).

  \[\text{RMSE} = \frac{1}{|\hat{R}|} \sum_{\hat{r}_{ui} \in \hat{R}}(r_{ui} - \hat{r}_{ui})^2.\]

  Parameters: | predictions (`list` of `Prediction`) – A list of predictions, as returned by the `test()` method. verbose – If True, will print computed value. Default is `True`.
  Returns: | The Mean Squared Error of predictions.
  Raises: | `ValueError` – When `predictions` is empty.

`surprise.accuracy.``rmse`(predictions, verbose=True)

  Compute RMSE (Root Mean Squared Error).

  \[\text{RMSE} = \sqrt{\frac{1}{|\hat{R}|} \sum_{\hat{r}_{ui} \in \hat{R}}(r_{ui} - \hat{r}_{ui})^2}.\]

  Parameters: | predictions (`list` of `Prediction`) – A list of predictions, as returned by the `test()` method. verbose – If True, will print computed value. Default is `True`.
  Returns: | The Root Mean Squared Error of predictions.
  Raises: | `ValueError` – When `predictions` is empty.