inst/shinyApp/Rmd-docs/MboPlotFit.md

In PhilippScheller/VisBayesOpt: Visualizing model based optimization runs from package mlrMBO

MboPlotFit

Description The plots show the fit of the model.

Interpretation * Left plot: Shows the in-sample R-squared at a certain iteration $$ R^2=1-\frac{SSR}{SST}=1-\frac{\sum_{i=1}^n (y_i-\hat y_i)^2}{\sum_{i=1}^n(y_i-\bar y)^2} $$ where: $y_i$  evaluated (true) target $\hat y_i$  predicted target based on surrogate $n$  number of iterations

• Right plot: Shows the predicted target $\hat y$ against the real target $y$. The length of the range corresponds to the estimated standard error (uncertainty) of the prediction of $\hat y$. The color corresponds to the iteration. The angle bisector shows the perfect fit ($\hat y_i - y = 0, \forall i=1,\ldots, n$).

How to use * Shows how well the surrogate model fits the real (unknown) objective function. * Bad model fit is identified by the following characteristics: * Left plot: If $R^2$ is low. * Right plot: If the points for higher iterations frequently (i.e. not only once which could be exploration) fall away from angle bisector. * Actions if bad fit identified: choose another surrogate model class to improve the quality of the surrogate fit and thus the overall optimization result.

Modifications * $highlight_iter$: We can set $highlight_iter$ in the sidebar panel if we are interested in a specific iteration to be highlighted. The right plot only shows the target ($(y, \hat y)$) up to the $highlight_iter$. * $predict_y_iter_surrogate$: We can set $predict_y_iter_surrogate = TRUE$ to predict all estimated target values $\hat y$ by using the surrogate model of the iteration $highlight_iter$. If $predict_y_iter_surrogate = FALSE$ the predicted target values $\hat y$ are taken from the design matrix, i.e. $\hat y^{(i)}$ is predicted by the surrogate model of iteration $i$ $\forall i=1,\ldots,highlight_iter$. * Choosing $predict_y_iter_surrogate = TRUE$ may result in a bad prediction of $\hat y$ if the surrogate of $highlight_iter$ is bad (e.g. constant).

PhilippScheller/VisBayesOpt documentation built on Sept. 14, 2020, 12:47 p.m.