Internal function that performs cross validation to determine reasonable default values for L1 penalty in a conditional logistic regression
default.lambda(X, Y, stratum, nfolds = 10, alpha = 1)A numeric value for lambda minimizing cross validated deviance.
A matrix of covariates, with the number of rows equaling the number of observations.
A binary response variable.
A numeric vector with stratum membership of each observation.
The number of folds used in cross-validation. Default is 10.
The elastic net mixing parameter, a number between 0 and 1. alpha=0 would give pure ridge; alpha=1 gives lasso. Pure ridge penalty is never obtained in this implementation since alpha must be positive.