(stock-and-flow ), - . (Stella, Vensim, iThink, Powersim ), - . . , .
. . 13.1 , Stella Powersim. (, ) . :
□ susceptible , (. .
);
□ infected , ;
□ recovered , ;
□ infection_rate ( 1) ;
□ recovery_rate ( 0 1) , ;
□ get_sick , ;
□ get_well , .
, . 13.1 , Stella Powersim :
d(susceptible)/dt = - get_sick;
d(infected)/dt = get_sick - get_well;
d(recovered)/dt = get_weli;
get_sick = f(infected, susceptible, infection_rate);
get_well = f(infected, recovery_rate).
, :
susceptible(t+At) = susceptible(t) - get_sick * At
, . ,
:
get_sick = infected * susceptible *infection_rate get_well = infected * recovery_rate
, , , , , .
, : (, ( , , , , ). , , . - . , . . . . , . . - (. . 13.1, ).
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