Sums, products, maxima and minima

sum(), prod(), max() and min() work on model expressions as they do on numbers: each combines all the elements of all its arguments into one value, so max(x, 0) is the largest of all the elements of x and 0. The arguments can be expressions, numbers or both, in any order: max(0, demand - stock) and max(demand - stock, 0) mean the same.

Usage

sum(..., na.rm = FALSE)

prod(..., na.rm = FALSE)

max(..., na.rm = FALSE)

min(..., na.rm = FALSE)

Arguments

...

Expressions, numbers, or both.

na.rm

Passed to base R when no argument is an expression, and ignored otherwise, since an expression has no missing values.

Value

An expression with one element when any argument is an expression; otherwise what base R returns.

Details

quicopt provides its own versions of these four functions, because base R would read max(0, x) with its numeric max() and stop with an error. Called without any expression, they are base R's functions, so loading the package changes nothing about how they work on numbers. R reports this when the package is attached, as these functions being masked from base.

The status of a model with max() or min() is "heuristic": a good answer, not a proven optimum.

Examples

m <- model()
stock <- num_var(m, "stock", lower = 0, upper = 100)
demand <- c(60, 80, 120)
max(0, demand - stock)          # the largest shortfall of the three
#> max(max(max(0, (60 - stock)), (80 - stock)), (120 - stock))
sum(2, stock)                   # 2 + stock
#> (2 + stock)
max(3, 7)                       # 7, as in base R
#> [1] 7