title: Setting how many samples the boot() function calls
body: <p>I would like to coerce the boot() function to pull a specific number of samples from the target data set. For example, if the dataset i'm bootstrapping is 100 values, I would like to bootstrap the mean using exactly 50 of those values for each iteration of the bootstrap call. Is this possible? The functionality I'm trying to replicate would look something like this:</p>
  
  <pre><code>x = runif(100)
  x2 = data.frame()
  for (i in 1:100) {
  x1 = sample(x,50, replace = TRUE)
  x2[i,1] = mean(x1)
  }
  </code></pre>
  
  <p>In the end, I'd like to perform somthing like the above function with many different levels of sampling. I'm currently doing something analagous to the above code nested within a for loop but it is VERY slow becaues of the size of the data sets I'm working with so I'm hoping boot() can do it faster.</p>
  
  <p>Thanks</p>