Figure 2. A SI 2-compartment model, with both input and output in compartment 1.

All kij >0 are unidentifiable; but volume V
1 and the three parameter combinations (combos)
, - k
11 ≡ k
01+ k
21 and - k
22 ≡ k
12+ k
02 are uniquely SI.

All kij >0 are unidentifiable; but volume V
1 and the three parameter combinations (combos)
, - k
11 ≡ k
01+ k
21 and - k
22 ≡ k
12+ k
02 are uniquely SI.