From ?summary
digits: integer, used for number formatting with ‘signif()’ (for
‘summary.default’) or ‘format()’ (for ‘summary.data.frame’).
tapply(edf$pri, edf$reg, summary, digits = 42)
## $Reg1
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## 8258.00 9021.25 9784.50 9784.50 10547.75 11311.00
## $Reg2
## Min. 1st Qu. Median Mean 3rd Qu. Max.
## 11123.0 11905.5 12688.0 12688.0 13470.5 14253.0