metaphors - What do R-rated and X-rated mean here?

  • Tim

    From a course website for Brownian Motion and Stochastic Calculus

    Recommended Reading: R-Rated

    • Stochastic Differential Equations: An Introduction with Applications (6th edition) by B. Oksendal
    • Brownian Motion by P. Morters and Y. Peres

    Recommended Reading: X-Rated

    • Continuous Martingales and Brownian Motion by D. Revuz and M. Yor
    • Brownian Motion and Stochastic Calculus by I. Karatzas and S. Shreve

    I was wondering what R-rated and X-rated mean here? I only know a little that they are normally used for film ratings. But I suspect the reference books are rated according to their rigorousness and/or difficulty?

  • Answers
  • J.R.

    To interpret what is meant here, I think you have to consider a synonym of X-rated: hard core.

    I would think that an “X-rated” book on stochastic modeling, then, would be “hard core.” In other words: chock full of intense math, and not very friendly toward the casual hobbyist. Another way to say this might be, “not for the faint of heart.” I can imagine someone issuing a warning: “Don't buy this book if you skipped the prerequisite course.” I'd expect such a text to be on the opposite side of the spectrum of where I'd find Math for Dummies, which, to extend the metaphor, would be a G-rated book.

  • mgb

    Yes it's a joke on the R (restricted) and X (adult) cinema classifications.

    It means the first two books are moderately complicated and the last two are much more intimidating. The term hard-core, also from the adult entertainment industry, is also used.

  • Related Question

    etymology - What is the origin and meaning of "coyote ugly"?
  • Questioner

    I overheard two scoundrels discussing one of their dates as being "coyote ugly".

  • Related Answers
  • The Raven

    This comes from the term "coyote date," in which an inebriated person awakens the following morning with a person of the opposite sex in bed. The protagonist's arm is pinned beneath the ugly person's body.

    Allegedly, a coyote, when caught in a steel-jawed trap, will gnaw off its own leg to escape.

    You can do the math from here.

  • morganpdx

    Other than the popularization of the term from the movie of the same name, I believe it derives from the behavior of coyotes, which (among other canines), when caught in a trap will gnaw off a leg in order to escape death. It describes a person (usually a woman) who is so undesirable that her partner (usually a guy) is willing to gnaw off the limb she is sleeping on in order to escape rather than waking her. The guy will usually find himself in this situation when, after a night of heavy drinking, he wakes up the next morning in the bed of a woman he does not remember meeting and has no desire of getting to know better.

  • oosterwal

    Along with the correct explanations of 'Coyote Ugly', as already provided by The Raven and morganpdx, the whole picture is not complete without giving the three rating levels of the unfortunate date: 'One-bagger', 'Two-bagger', and 'Coyote Ugly'.

    One-bagger describes someone so uncomely that they are made to wear a bag over their head so that you don't have to look at their face while copulating.

    Two-bagger describes a person who is so much more distasteful that not only do you require them to wear a bag over their head, but you don one yourself in case the bag over their head falls off.

    Coyote Ugly, the worst of the three levels, has already been explained.