[R] Small p from binomial probability function.
Rolf Turner
r.turner at auckland.ac.nz
Thu Oct 17 00:15:58 CEST 2013
On 10/16/13 23:56, Benjamin Ward (ENV) wrote:
> Hi,
>
> Thanks again for your answers, just so as I can get clear what is happening, with the uniroot method, I'm defining a function in which the binomial probability function pbinom is present but in addition p0 is subtracted from the result - in this case p0 is the large P I want to plug in so 0.05, 0.50 and 0.95, or even just 0.05 and 0.95? Then uniroot finds the root of this function and doing so find me the small p I need?
I believe that you have a correct understanding. To beat it to death:
* you want/need to solve an equation of the form
f(p) = p0
for p.
* the uniroot() function solves equations of the form
g(p) = 0
for p
* therefore define g(p) = f(p) - p0 and apply uniroot() to the
function g(.).
HTH.
cheers,
Rolf Turner
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