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查stata的function啊
exp(x)
Title
[D] functions -- Functions
Description
This is a quick reference for the mathematical functions. For help on all functions, see [D] functions.
Mathematical functions
abs(x)
Domain: -8e+307 to 8e+307
Range: 0 to 8e+307
Description: returns the absolute value of x.
acos(x)
Domain: -1 to 1
Range: 0 to pi
Description: returns the radian value of the arccosine of x.
acosh(x)
Domain: 1 to 8.9e+307
Range: 0 to 709.77
Description: returns the inverse hyperbolic cosine of x,
acosh(x) = ln{x+sqrt(x*x - 1)}.
asin(x)
Domain: -1 to 1
Range: -pi/2 to pi/2
Description: returns the radian value of the arcsine of x.
asinh(x)
Domain: -8.9e+307 to 8.9e+307
Range: -709.77 to 709.77
Description: returns the inverse hyperbolic sine of x,
asinh(x) = ln{x+sqrt(x*x + 1)}.
atan(x)
Domain: -8e+307 to 8e+307
Range: -pi/2 to pi/2
Description: returns the radian value of the arctangent of x.
atan2(y,x)
Domain y: -8e+307 to 8e+307
Domain x: -8e+307 to 8e+307
Range: -pi to pi
Description: returns the radian value of the arctangent of y/x, where the signs of the parameters y and x
are used to determine the quadrant of the answer.
atanh(x)
Domain: -1 to 1
Range: -8e+307 to 8e+307
Description: returns the inverse hyperbolic tangent of x, atanh(x) = (1/2){ln(1+x) - ln(1-x)}.
ceil(x)
Domain: -8e+307 to 8e+307
Range: integers in -8e+307 to 8e+307
Description: returns the unique integer n such that n - 1 < x < n.
returns x (not ".") if x is missing, meaning that ceil(.a) = .a.
Also see floor(x), int(x), and round(x).
cloglog(x)
Domain: 0 to 1
Range: -8e+307 to 8e+307
Description: returns the complementary log-log of x,
cloglog(x) = ln{-ln(1-x)}.
comb(n,k)
Domain n: integers 1 to 1e+305
Domain k: integers 0 to n
Range: 0 to 8e+307 and missing
Description: returns the combinatorial function n!/{k!(n - k)!}.
cos(x)
Domain: -1e+18 to 1e+18
Range: -1 to 1
Description: returns the cosine of x, where x is in radians.
cosh(x)
Domain: -709 to 709
Range: 1 to 4.11e+307
Description: returns the hyperbolic cosine of x,
cosh(x) = {exp(x) + exp(-x)}/2.
digamma(x)
Domain: -1e+15 to 8e+307
Range: -8e+307 to 8e+307 and missing
Description: returns the digamma() function. This is the derivative of lngamma(x).
The digamma(x) function is sometimes called the psi function.
exp(x)
Domain: -8e+307 to 709
Range: 0 to 8e+307
Description: returns the exponential function of e^x. This function is the inverse of ln(x).
floor(x)
Domain: -8e+307 to 8e+307
Range: integers in -8e+307 to 8e+307
Description: returns the unique integer n such that n < x < n + 1.
returns x (not ".") if x is missing, meaning that floor(.a) = .a.
Also see ceil(x), int(x), and round(x).
int(x)
Domain: -8e+307 to 8e+307
Range: integers in -8e+307 to 8e+307
Description: returns the integer obtained by truncating x toward 0; thus,
int(5.2) = 5
int(-5.8) = -5
returns x (not ".") if x is missing, meaning that int(.a) = .a.
One way to obtain the closest integer to x is int(x+sign(x)/2), which simplifies to
int(x+0.5) for x > 0. However, use of the round() function is preferred. Also see round(x),
ceil(x), and floor(x).
invcloglog(x)
Domain: -8e+307 to 8e+307
Range: 0 to 1 and missing
Description: returns the inverse of the complementary log-log function of x,
invcloglog(x) = 1 - exp{-exp(x)}.
invlogit(x)
Domain: -8e+307 to 8e+307
Range: 0 to 1 and missing
Description: returns the inverse of the logit function of x,
invlogit(x) = exp(x)/{1 + exp(x)}.
ln(x)
Domain: 1e-323 to 8e+307
Range: -744 to 709
Description: returns the natural logarithm, ln(x). This function is the inverse of exp(x).
lnfactorial(n)
Domain: integers 0 to 1e+305
Range: 0 to 8e+307
Description: returns the natural log of n factorial = ln(n!).
To calculate n!, use round(exp(lnfactorial(n)),1) to ensure that the result is an integer.
Logs of factorials are generally more useful than the factorials themselves because of
overflow problems.
lngamma(x)
Domain: -2,147,483,648 to 1e+305 (excluding negative integers)
Range: -8e+307 to 8e+307
Description: returns the natural log of the gamma function of x. For integer values of x > 0, this is
ln((x-1)!).
lngamma(x) for x < 0 returns a number such that exp(lngamma(x)) is equal to the absolute
value of the gamma function. That is, lngamma(x) always returns a real (not complex) result.
log(x)
Domain: 1e-323 to 8e+307
Range: -744 to 709
Description: returns the natural logarithm, ln(x), which is a synonym for ln(x).
log10(x)
Domain: 1e-323 to 8e+307
Range: -323 to 308
Description: returns the base-10 logarithm of x.
logit(x)
Domain: 0 to 1 (exclusive)
Range: -8e+307 to 8e+307 and missing
Description: returns the log of the odds ratio of x,
logit(x) = ln{x/(1-x)}.
max(x1,x2,...,xn)
Domain x1: -8e+307 to 8e+307 and missing
Domain x2: -8e+307 to 8e+307 and missing
...
Domain xn: -8e+307 to 8e+307 and missing
Range: -8e+307 to 8e+307 and missing
Description: returns the maximum value of x1, x2, ..., xn. Unless all arguments are missing, missing
values are ignored.
max(2,10,.,7) = 10
max(.,.,.) = .
min(x1,x2,...,xn)
Domain x1: -8e+307 to 8e+307 and missing
Domain x2: -8e+307 to 8e+307 and missing
...
Domain xn: -8e+307 to 8e+307 and missing
Range: -8e+307 to 8e+307 and missing
Description: returns the minimum value of x1, x2, ..., xn. Unless all arguments are missing, missing
values are ignored.
min(2,10,.,7) = 2
min(.,.,.) = .
mod(x,y)
Domain x: -8e+307 to 8e+307
Domain y: 0 to 8e+307
Range: 0 to 8e+307
Description: returns the modulus of x with respect to y. mod(x,y) = x - y*floor(x/y)
mod(x,0) = .
reldif(x,y)
Domain x: -8e+307 to 8e+307 and missing
Domain y: -8e+307 to 8e+307 and missing
Range: -8e+307 to 8e+307 and missing
Description: returns the "relative" difference |x-y|/(|y|+1).
returns 0 if both arguments are the same type of extended missing value.
returns missing if only one argument is missing or if the two arguments are two different
types of missing.
round(x,y) or round(x)
Domain x: -8e+307 to 8e+307
Domain y: -8e+307 to 8e+307
Range: -8e+307 to 8e+307
Description: returns x rounded in units of y or x rounded to the nearest integer if the argument y is
omitted.
returns x (not ".") if x is missing, meaning that round(.a) = .a and round(.a,y) = .a if y is
not missing; if y is missing, "." is returned.
For y = 1, or with y omitted, this amounts to the closest integer to x; round(5.2,1) is 5, as
is round(4.8,1); round(-5.2,1) is -5, as is round(-4.8,1). The rounding definition is
generalized for y != 1. With y = .01, for instance, x is rounded to two decimal places;
round(sqrt(2),.01) is 1.41. y may also be larger than 1; round(28,5) is 30, which is 28
rounded to the closest multiple of 5. For y = 0, the function is defined as returning x
unmodified. Also see int(x), ceil(x), and floor(x).
sign(x)
Domain: -8e+307 to 8e+307 and missing
Range: -1, 0, 1 and missing
Description: returns the sign of x: -1 if x < 0, 0 if x = 0, 1 if x > 0, and missing if x is missing.
sin(x)
Domain: -1e+18 to 1e+18
Range: -1 to 1
Description: returns the sine of x, where x is in radians.
sinh(x)
Domain: -709 to 709
Range: -4.11e+307 to 4.11e+307
Description: returns the hyperbolic sine of x,
sinh(x) = {exp(x) - exp(-x)}/2.
sqrt(x)
Domain: 0 to 8e+307
Range: 0 to 1e+154
Description: returns the square root of x.
sum(x)
Domain: all real numbers and missing
Range: -8e+307 to 8e+307 (excluding missing)
Description: returns the running sum of x, treating missing values as zero.
For example, following the command generate y=sum(x), the jth observation on y contains the
sum of the first through jth observations on x. See [D] egen for an alternative sum
function, total(), that produces a constant equal to the overall sum.
tan(x)
Domain: -1e+18 to 1e+18
Range: -1e+17 to 1e+17 and missing
Description: returns the tangent of x, where x is in radians.
tanh(x)
Domain: -8e+307 to 8e+307
Range: -1 to 1 and missing
Description: returns the hyperbolic tangent of x,
tanh(x) = {exp(x) - exp(-x)}/{exp(x) + exp(-x)}.
trigamma(x)
Domain: -1e+15 to 8e+307
Range: 0 to 8e+307 and missing
Description: returns the second derivative of lngamma(x). The trigamma() function is the derivative of
digamma(x).
trunc(x) is a synonym for int(x).
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