R help - May 2008 - (1-alpha)th percentile

hello;
firstly, my gratitude to all who help me to find a function that allows me
to add confidence interval to my graph.  
in order to calculate the (1-alpha)th percentile of for exemple an
F(df1,df2) distribution i do like this:
v<-df(alpha,df1,df2)
percentile<-qf(v,df1,df2,alpha)

if it is true please alert me , and if it is not what should do then?

:handshake:
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hanen <hanen.mastouri <at> yahoo.fr> writes:
> 
> 
> hello;
> firstly, my gratitude to all who help me to find a function that allows me
> to add confidence interval to my graph.  
> in order to calculate the (1-alpha)th percentile of for exemple an
> F(df1,df2) distribution i do like this:
> v<-df(alpha,df1,df2)
> percentile<-qf(v,df1,df2,alpha)
> 
> if it is true please alert me , and if it is not what should do then?
> 
> :handshake:

   I think it's just qf(1-alpha,df1,df2)

   To use a well-known example:
qnorm(0.975) = 1.959964
(in this case, for a two-tailed test, you need 1-alpha/2 , but
F is one-tailed so that's no problem.

  Ben Bolker