Program simple simulation in R

Question

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

Did you notice that, since `C < D`, `rnum[i] < C` is always `TRUE` if `rnum[i] < D`? — Sven Hohenstein, Nov 30 '13 at 19:17
when the condition rnum[i] < C is met, the function should put -5 into the row. D only comes into play in subsequent rows, so i do not think your concern is a problem. — user2813055, Nov 30 '13 at 19:24

score 0 · Answer 1 · answered Nov 30 '13 at 19:03

0

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)))

answered Nov 30 '13 at 19:03

agstudy

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How does this bit of code take into account previous rows? When rnum=D, can you explain where your code does this? – user2813055 Nov 30 '13 at 20:25
@user2813055 I think I miss something. You should provide a reproducible example with the expected output. please read [this](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) – agstudy Nov 30 '13 at 21:31

Program simple simulation in R

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