I am in the process of adding tests to my R package iemisc. Previously, I created functions to use degrees rather than radians for trigonometric functions.
Is there a method to determine if a given number is in radians versus degrees?
If so, then I would like to incorporate that method in my tests.
For example, based off of the recent Win-Vector Blog article written by John Mount, http://www.win-vector.com/blog/2019/03/unit-tests-in-r/, and the RUnit vignette, I wrote the following test for cosd:
test_cosd <- function() {
library("iemisc")
RUnit::checkEquals(cosd(360), 1)
RUnit::checkEquals(cosd(90), 0)
RUnit::checkEquals(cosd(0), 1)
RUnit::checkException(cosd(pi * 3 / 4))
RUnit::checkException(cosd("sq"))
invisible(NULL)
}
However, I would like to have a checkException for numbers that are radian measurements rather than degrees measurements.
Thank you.
It is possible to take advantage of the difference in magnitude between the measures to make reasonable inference about whether the input is degrees or radians. A measurement in degrees is about 60 times the size of the same measurement in radians. This can be seen from the underlying relationship:
180 degrees = pi (3.14159) radians
There is a simple heuristic possible, if you can safely assume users will use the tool only with angles smaller than a full circle (not unreasonable in many physical product engineering applications, unless corkscrew helices are involved). In that case, it would be safe to assume values greater than 2*pi, or 6.28 represents degrees.
Otherwise, the values themselves are indistinguishable.