Applying a function to a vector

I have defined a function to compute the value of a
beta distribution of the second kind (the existing
beta distribution of th stats package is the beta
distribution of the first kind). It works perfectly
for a single value, but I want to apply it to a vector
of 22 000 values. I can use a loop for the calculation
of each value but it runs very very slowly.
So, what can I change ?

Hers's the function : 
p <-  c(1,1)
y <-  1
z <-  1
truc  <-  function(y)  {y^(p[1]-1)/(1+y)^(p[1]+p[2])}
pbeta2  <-  function(z,p)
1/beta(p[1],p[2])*integrate(truc,0,z)$value

machin <- pbeta2(vector,p) just return a single value

Thanks for your help