Hi, I want to run something like
  SELECT firm_id, count(*), mean(value), sd(value)
  FROM table
  GROUP BY firm_id;

But I have to write a for loop like
  for ( id in unique(table$firm_id ) {
    print(paste(  id, mean(table[firm_id == id, "value"])  ))
  }

Is there any way to do it easier? Thanks :)


Best,
Reeyarn Lee

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