Society of Actuaries (SOA) PA Practice Exam

The command to graph the ROC (Receiver Operating Characteristic) curve is indeed achieved by using the function `plot()` on the ROC object that was created using the `roc()` function from the `pROC` package in R. The `roc()` function calculates necessary statistics and generates an object containing the data needed to visualize the ROC curve. Once the ROC object is created, calling `plot()` on it effectively generates the graphical representation of the curve.

This approach separates the data preparation from the visualization process, making it clearer and more modular. Essentially, the `roc(data)` function prepares the ROC data that will be plotted, and `plot(roc)` is what you use to visualize this data on a graph. This clear distinction allows for more flexibility in handling ROC analysis and plotting in R.

The other options do not correspond to the correct method of graphing the ROC curve in R. For example, `roc(data)` is meant for calculating the ROC statistics, not for plotting. Similarly, `curve(roc)` and `draw(roc)` are not standard functions in R used for creating ROC curves, thereby making those incorrect choices for the task at hand.