Program simple simulation in R

问题

Editing this post for simplification according to @agstudy

I am trying to develop a model that simulates a polymer using a random uniform distribution.

The model has 2 states

State 1 (probability of state 1 if in state 2 is .003): growth probability, A = .01 shrink probability, B = .0025

State 2 (probability of state 2 if in state 1 is .0003): growth probability, A = .01 shrink probability, E = .05

Simulation starts in State 1

While in State 1, sample random numbers from data.frame1, if # < .0025 input -1 in data.frame2, if # < .01 input +1 in data.frame2, if neither input 0 in data.frame2. continue until reaching # < .0003 (probability to enter state 1)

If # < .0003 is sampled, input -1 into data.frame2, and switch to state 2. continue sampling random numbers, while in state 2 if # < .003 input +1 into data.frame2 and switch to State 1 and proceed as indicated above. If in state 2 the # >= .003, and if # < .05 input -1 into data.frame2, else input 0 in data.frame2

I hope this clears things up @agstudy, but there is a chance it might not… sorry if that is the case.

here is an example generated in excel of how a small set should look

the 1st column would be from data.frame1 and the input column would be data.frame2, i included state and length column for explanatory purposes.

    rnumbers  state input length
    0           1   0   0 # initialized state
    0.009413895 1   1   1
    0.052959306 1   1   2
    0.002453354 1   -1  1
    0.000290324 2   -1  0
    0.093312954 2   0   0
    0.077210941 2   0   0
    0.04924944  2   -1  -1
    0.010590107 2   -1  -2
    0.03308292  2   -1  -3
    0.037239807 2   -1  -4
    0.007889393 2   -1  -5
    0.026476751 2   -1  -6
    0.000454509 1   1   -5
    0.009820683 1   1   -4
    0.019836999 1   1   -3
    0.009380381 1   1   -2
    0.083149383 1   1   -1
    0.022212547 1   1   0
    0.051917035 1   1   1
    0.05032031  1   1   2
    0.03956718  1   1   3
    0.032664445 1   1   4
    0.004352291 1   1   5
    0.08902418  1   1   6
    0.095643962 1   1   7

回答1:

I would write something like this:

step_generator <- function(rnum)
   ifelse(rnum<C,
       ifelse(rnum>=D,-5,ifelse(rnum<B,-1,ifelse(rnum<A,1,0))),
       ifelse(rnum<B,-1,ifelse(rnum<A,1,0)))

来源：https://stackoverflow.com/questions/20304101/program-simple-simulation-in-r