Table 1 Alternative ways to describe populations.
From: PopMod: a longitudinal population model with two interacting disease states
| Logical expression | Meaning | Differential equations expression |
|---|---|---|
| ~ X~ C | Population group with neither X nor C | S |
| X~ C | Population group with X but not C, i.e. with X only | X |
| ~ XC | Population group with C but not X, i.e. with C only | C |
| ~ X | Population group without X | S + C |
| ~ C | Population group without C | S + X |
| X | Total population group with X | X + XC |
| C | Total population group with C | C + XC |
| S | Susceptible population | S |
| XC | Population with both X and C | XC |
| T | Total population | T |