```
set.seed(17)
piz <- d.pizza[sample(nrow(d.pizza),10), c("temperature","price","driver","weekday")]
f1 <- formula(. ~ driver)
f2 <- formula(temperature ~ .)
f3 <- formula(temperature + price ~ .)
f4 <- formula(temperature ~ . - driver)
f5 <- formula(temperature + price ~ driver)
f6 <- formula(temperature + price ~ driver * weekday)
f7 <- formula(I(temperature^2) + sqrt(price) ~ driver + weekday)
f8 <- formula(temperature + price ~ 1)
f9 <- formula(temperature + price ~ driver * weekday - price)
ParseFormula(f1, data=piz)
ParseFormula(f2, data=piz)
ParseFormula(f3, data=piz)
ParseFormula(f4, data=piz)
ParseFormula(f5, data=piz)
ParseFormula(f6, data=piz)
ParseFormula(f7, data=piz)
ParseFormula(f8, data=piz)
```

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