Return missing information about a line — solve

Takes a set of inputs that is sufficient information to infer a line and then returns information not provided (either the slope, an x point on the line, or a y point on the line)

Usage

solve_linear(
  x1,
  y1,
  x2 = NULL,
  y2 = NULL,
  x3 = NULL,
  y3 = NULL,
  m = NULL,
  named = TRUE
)

Arguments

x1, y1: A point on the line
x2, y2: An additional point on the line
x3, y3: An additional point on the line
m: The slope of the line
named: logical indicating whether the returned value(s) should be named according to what they are (m, x2, y2, x3, or y3)

Value

A named vector with the missing information from the line:

If m and x2 are provided, y2 will be returned

If m and y2 are provided, x2 will be returned

If x2 and y2 are provided, but neither x3 nor y3 are provided, m will be returned

If x2 and y2 are provided and one of x3 or y3 are provided, the other (y3 or x3) will be returned

Details

Note that there is no requirement that x1 < x2 < x3: the points can be in any order along the line.

solve_linear works with vectors of all inputs to solve multiple lines at once, where the ith element of each argument corresponds to the ith output. Note that all lines must be missing the same information. Input vectors will be recycled as necessary.