Replace negative values by zero

We want to set all values in an array zero that are negative.

I tried out a a lot of stuff but did not yet achieve a working solution. I thought about a for loop with condition, however this seems not to work.

#pred_precipitation is our array
pred_precipitation <-rnorm(25,2,4)     

for (i in nrow(pred_precipitation))
{
  if (pred_precipitation[i]<0) {pred_precipitation[i] = 0}
  else{pred_precipitation[i] = pred_precipitation[i]}
}