[R] Coverage Probability
Hello.
I'm allready this far. I have a function which is calculating the lower (l)
and upper (u) limit for a confidence interval for the odds ratio.
For example for 5 simulated 2x2 tables the upper and lower limits are:
u
[1] 2.496141 7.436524 8.209161 4.313587 3.318612
l
[1] -0.9718608 1.1000713 1.5715373 0.1135158 -0.2700517
With (l[1]; u[1]) being the confidence interval for the odds ratio for the
first simulated table and so on.
Now I want to compute the coverage probability. For that I've created a
function which is return 1 if the odds ratio is in the interval and 0 if it
isn't.
cover - function(theta, u, l){
if(theta = l theta = u){z=1}
if(theta l || thetau){z=0}; return(z)
}
This works but unfortunately not if I want to summarize the function and
divide it with the sample size to get the coverage probability.
I tried it this way
for(for(x in 1:5) {a = (sum(cover(theta, u[x], l[x]))/5; return(a)}
Maybe someone can help me. Thank you
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Re: [R] Coverage Probability
Thank you very much. This was, was i needed. Unfortunately I have one futher
problem with this Code. I don't only need the coverage probability for one
but for a range of different odds ratios. (for example [1;30]). I tried it
with a loop but I get an error. I think again, that I'm almost there but
having a little mistake. The complete code is:
#setting values
n1 - 10
n2 - 10
y - 100
alpha - 1
z-1.96
# creating 2x2 table
for (i in 1:30)
{
theta - i
x1 - exp(alpha +theta)/ (1+ exp(alpha +theta))
x2 - exp(alpha)/ (1+ exp(alpha))
n11 - rbinom(y, 10, x1)
n12 - n1 - n11
n21 - rbinom(y, 10, x2)
n22 - n2 - n21
# upper and lower limit gart interval
gartu -function(z,d,e, f, g){log(((d+.5)*(g+.5))/((e+.5)*(f+.5)))+
z*sqrt(1/(d+.5)+1/(e+.5)+1/(f+.5)+1/(g+.5))}
gartl -function(z,d,e, f, g){log(((d+.5)*(g+.5))/((e+.5)*(f+.5)))-
z*sqrt(1/(d+.5)+1/(e+.5)+1/(f+.5)+1/(g+.5))}
u - gartu(z, n11[i],n22[i],n12[i],n21[i])
l - gartl(z, n11[i],n22[i],n12[i],n21[i])
foo - function(theta, u, l) mean(theta = l theta = u, na.rm = TRUE)
foo(theta, u, l)
}
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Re: [R] Coverage Probability
Thank you very much again. But in this case I get the coverage probability as an average over all values for the odds ratio. I need a coverage probability for every value for the odds ratio. So the coverage probability for odds ratio = 1, than for odds ratio = 2 and so on. Sorry to bother you again but I have some problems with loops. -- View this message in context: http://r.789695.n4.nabble.com/Coverage-Probability-tp4485511p4486264.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
[R] Simulating n 2x2 tables with the same odds ratio
Hello. I'm looking for a method to simulate n different 2x2 tables having all the same odds ratio. For example. I need 100 tables with odds ratio 1 100 tables with odds ratio 2 100 tables with odds ratio 3 and so on. All tables should have the same marginal frequencies. Thank you -- View this message in context: http://r.789695.n4.nabble.com/Simulating-n-2x2-tables-with-the-same-odds-ratio-tp4459457p4459457.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
