Built-in Functions
All the mathematical functions you could ever want are here (see Table 2.1). The log function gives logs to the base e e = 2 718282, for which the antilog function is exp
log(10) [1] 2.302585 exp(1) [1] 2.718282
If you are old fashioned, and want logs to the base 10, then there is a separate function
log 10(6) [1] 0.7781513
Logs to other bases are possible by providing the log function with a second argument which is the base of the logs you want to take. Suppose you want log to base 3 of 9:
log(9,3) [1] 2
The trigonometric functions in R measure angles in radians. A circle is 2π radians, and this is 360°, so a right angle (90°) is π/2 radians. R knows the value of π as pi:
pi [1] 3.141593 sin(pi/2) [1] 1 cos(pi/2) [1] 6.123032e-017
Notice that the cosine of a right angle does not come out as exactly zero, even though the sine came out as exactly 1. The e–017 means ‘times 10−17’. While this is a very smallnumber it is clearly not exactly zero (so you need to be careful when testing for exact equality of real numbers; see p. 77).
Function | Meaning |
log(x) | log to base e of x |
exp(x) | antilog of x(ex) |
log(x,n) | log to base n of x |
log10(x) | log to base 10 of x |
sqrt(x) | square root of x |
factorial(x) | x! |
choose(n,x) | binomial coefficients n!/(x! (n – x)!) |
gamma(x) | Γ(x), for real x(x – 1)!, for integer x |
lgamma(x) | natural log of Γ(x) |
floor(x) | greatest integer < x |
ceiling(x) | smallest integer > x |
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