I want to change the specific components of R's two-dimensional array.

I'd like to make all values that appear more than 10 times from 2D array a random. How should I describe them?I want to do it without looping.
For writing using the for statement,

for(time in unique(a)){
  if(length(a[a==time])>=10){
    a[a==time]<-0
  }
}

I think I can write like that, but I don't know how to make it happen without using a loop.The work we're doing now involves a large number of two-dimensional arrays, so we're looking for ways to achieve this without looping as much as possible.
If you are familiar with the description of R, please take care of it.