* Point cloud metrics are directly computed from the point cloud or from the derived surface model on the whole plot extent. These are the metrics generally used in the area-based approach.
+ Tree metrics are computed from the characteristics of trees detected in the point cloud (or in the derived surface model). They are more CPU-intensive to compute and require ALS data with higher density, but in some cases they allow a slight improvement in models prediction accuracy.
## Point cloud metrics
Point cloud metrics are computed with the function `lidaRtRee::clouds_metrics`, which applies the `lidR::cloud_metrics` to all point clouds in the list. Default computed metrics are those proposed by the function [`lidR::stdmetrics`](https://github.com/Jean-Romain/lidR/wiki/stdmetrics). Additional metrics are available with the function `lidaRtRee::ABAmodelMetrics`.
Point cloud metrics are computed with the function `lidaRtRee::clouds_metrics`, which applies the `lidR::cloud_metrics` to all point clouds in a list. Default computed metrics are those proposed by the function [`lidR::stdmetrics`](https://github.com/Jean-Romain/lidR/wiki/stdmetrics). Additional metrics are available with the function `lidaRtRee::aba_metrics`. The buffer points, which are located outside of the plot extent inventoried on the field, should be removed before computing those metrics
Once a dependent variable (forest parameter of interest) has been chosen, the function `lidaRtRee::ABAmodel` is used to select the linear regression model that yields the highest adjusted-R^2^ with a defined number of independent variables, while checking linear model assumptions. A Box-Cox transformation of the dependent variable can be applied to normalize its distribution, or a log transformation of all variables (parameter `transform`). Model details and cross-validation statistics are available from the returned object.
Once a dependent variable (forest parameter of interest) has been chosen, the function `lidaRtRee::aba_build_model` is used to select the linear regression model that yields the highest adjusted-R^2^ with a defined number of independent variables (metrics), while checking linear model assumptions. A Box-Cox transformation of the dependent variable can be applied to normalize its distribution, or a log transformation of all variables (parameter `transform`). Model details and cross-validation statistics are available from the returned object.
@@ -243,7 +248,7 @@ When calibrating a statistical relationship between forest stand parameters, whi
Stratum-specific models are computed and stored in a list during a `for` loop. The function `lidaRtRee::aba_combine_strata` then combines the list of models corresponding to each stratum to compute aggregated statistics for all plots, making it easier to compare stratified with non-stratified models.
In this example, the model for "private" yields a large error on the plot "Verc-C5-1", which considerably lowers the accuracy of the stratified approach.
In this example, the model for "private" ownership yields a large error on the plot "Verc-C5-1", which considerably lowers the accuracy of the stratified approach.
To avoid applying models in non-forest areas and to remove the extremes values that may have been predicted due to outliers in the ALS and metrics values, the function `lidaRtRee::clean_raster` can be applied:
To avoid applying models in non-forest areas and to remove the extremes values that may have been predicted due to outliers in the ALS point cloud and metrics values, the function `lidaRtRee::clean_raster` can be applied:
* it applies a lower and upper threshold to map values,