One of seven possible options: "all" to display 5 traces in one graph,
"seq" to display 5 full-sized traces in sequence in response to user prompts,
"coef" to display only the estimated beta coefficient trace,
"rmse" to display only the estimated relative MSE risk trace,
"exev" to display only the estimated excess MSE eigenvalue (OLS minus larlso),
"infd" to display only the estimated inferior direction cosine trace, or
"spat" to display only the delta-factor pattern trace.