Within the framework of the paper, r is the total number of lambda*f terms. If force = "two-way" is on, I would think that the first and second factors are the unit and time fixed effects, and so r must be 2 or higher, but cross validation finds r=0 or r=1 sometimes. Does the "r" found by cross validation indicate the number of factors IN ADDITION to the unit and fixed effects when force="two-way"?
Within the framework of the paper, r is the total number of lambda*f terms. If force = "two-way" is on, I would think that the first and second factors are the unit and time fixed effects, and so r must be 2 or higher, but cross validation finds r=0 or r=1 sometimes. Does the "r" found by cross validation indicate the number of factors IN ADDITION to the unit and fixed effects when force="two-way"?