IrregFunData:
3 observations of 1-dimensional support on 5 different argvals (3 - 5 per curve).

@argvals: List of 3
 $ : int [1:5] 1 2 3 4 5
 $ : int [1:3] 2 3 4
 $ : int [1:3] 3 4 5

@X: List of 3
 $ : int [1:5] 1 2 3 4 5
 $ : int [1:3] 2 3 4
 $ : int [1:3] -3 -2 -1
