What does the variable "k" stand for?

Question

I use the tween.js library, it contains some built in easing functions such as this one:

Quadratic: {
    In: function (k) {
        return k * k;
    }
};

The user guide describes the variable k as:

k: the easing progress, or how far along the duration of the tween we are. Allowed values are in the range [0, 1].

My question is why k, what does this letter stand for? If I'd written the function myself, I'd have named it p meaning either progress or percentage.

it is just a variable, why it matters for you? :) `k` `p` `something` - who cares — Andrew Evt, Nov 04 '15 at 18:54
@AndrewEvt Dosn't matter, just curious - Plan on learning something new today. Perhaps someone will tell me something about the letter k that will blow my mind. — Drahcir, Nov 04 '15 at 18:54
@AndrewEvt: Variable names *do* matter. The 'who cares?' attitude towards variable names, which often carries over to naming in general (e.g. functions, classes, etc.), is one contributor for code that is more difficult to understand and maintain. The OP's post is merely additional evidence of this. — code_dredd, Nov 04 '15 at 18:57
The only person who can reasonably answer this question is the person who chose the letter `k`. — T.J. Crowder, Nov 04 '15 at 18:59
Could it be that it is minified? In other words, the minification engine arbitrarily replaced a meaningful name such as `progress` with the letter `k`? Just guessing. — Stack0verflow, Nov 04 '15 at 19:01
@FelixKling Good sugggestion, have made an issue: https://github.com/tweenjs/tween.js/issues/233 — Drahcir, Nov 04 '15 at 19:02
@T.J.Crowder Yeah, I agree. I just thought maybe there was an obvious reason for it. — Drahcir, Nov 04 '15 at 19:02
the letter k is frequently used in mathematical formulas along with x,y,n,p etc as in f (k) = p (1-p) k. It is possible the creator extrapolated the f(k) for his usage to be function (k) for this API. — Brian from state farm, Nov 04 '15 at 19:24
Maybe the programmer was racist/mischievous and liked to see kkk in the code. — AwokeKnowing, Nov 04 '15 at 20:35

Moob · Answer 1 · 2015-11-04T20:55:47.460

This Wikipedia article on naming conventions in mathematics (https://en.m.wikipedia.org/wiki/Latin_letters_used_in_mathematics) tells us that the lower case k represents:

• the unit prefix kilo- (10³)

• the Boltzmann constant, this is often represented as kB to avoid confusion with

•the Wavenumber of the wave equation

•an integer, e.g. a dummy variable in summations, or an index of a matrix.

•an unspecified (real) constant

•the spring constant of Hooke's law

•the spacetime Curvature from the Friedmann equations in cosmology

I would suggest that the fourth item is the most appropriate description of k in this instance.

an integer, e.g. a dummy variable in summations, or an index of a matrix.

If the author had reason to name the variable k perhaps this is it. If so, then 'k' doesn't 'stand for' anything but is merely a convention used by maths nerds ;)

score 2 · Accepted Answer · answered Nov 05 '15 at 00:02

2

Alright, I wrote the code (a classic simplification of the classic Penner easing equations), and honestly I don't remember why I chose k. It used to be my default variable name for a ratio between 0 and 1. No good reason come to my mind.

answered Nov 05 '15 at 00:02

Philippe

2,621
1
19
20

1

Thanks for taking the time to answer such an odd question :) – Drahcir Nov 05 '15 at 09:03

What does the variable "k" stand for?

2 Answers2