math module¶
datatable
provides the similar set of mathematical functions, as Python’s
standard math module, or numpy math functions. Below is the comparison
table showing which functions are available:
math  numpy  datatable 

Trigonometric/hyperbolic functions  
sin(x) 
sin(x) 
sin(x) 
cos(x) 
cos(x) 
cos(x) 
tan(x) 
tan(x) 
tan(x) 
asin(x) 
arcsin(x) 
arcsin(x) 
acos(x) 
arccos(x) 
arccos(x) 
atan(x) 
arctan(x) 
arctan(x) 
atan2(y, x) 
arctan2(y, x) 
arctan2(y, x) 
sinh(x) 
sinh(x) 
sinh(x) 
cosh(x) 
cosh(x) 
cosh(x) 
tanh(x) 
tanh(x) 
tanh(x) 
asinh(x) 
arcsinh(x) 
arsinh(x) 
acosh(x) 
arccosh(x) 
arcosh(x) 
atanh(x) 
arctanh(x) 
artanh(x) 
hypot(x, y) 
hypot(x, y) 
hypot(x, y) 
radians(x) 
deg2rad(x) 
deg2rad(x) 
degrees(x) 
rad2deg(x) 
rad2deg(x) 
Exponential/logarithmic/power functions  
exp(x) 
exp(x) 
exp(x) 
exp2(x) 
exp2(x) 

expm1(x) 
expm1(x) 
expm1(x) 
log(x) 
log(x) 
log(x) 
log10(x) 
log10(x) 
log10(x) 
log1p(x) 
log1p(x) 
log1p(x) 
log2(x) 
log2(x) 
log2(x) 
logaddexp(x, y) 

logaddexp2(x, y) 

cbrt(x) 
cbrt(x) 

pow(x, a) 
power(x, a) 
power(x, a) 
sqrt(x) 
sqrt(x) 
sqrt(x) 
square(x) 
square(x) 

Special mathematical functions  
erf(x) 
erf(x) 

erfc(x) 
erfc(x) 

gamma(x) 
gamma(x) 

heaviside(x) 

i0(x) 

lgamma(x) 
lgamma(x) 

sinc(x) 

Floatingpoint functions  
ceil(x) 
ceil(x) 
ceil(x) 
copysign(x, y) 
copysign(x, y) 

fabs(x) 
fabs(x) 
fabs(x) 
floor(x) 
floor(x) 
floor(x) 
frexp(x) 
frexp(x) 

isclose(x, y) 
isclose(x, y) 

isfinite(x) 
isfinite(x) 
isfinite(x) 
isinf(x) 
isinf(x) 
isinf(x) 
isnan(x) 
isnan(x) 
isna(x) 
ldexp(x, n) 
ldexp(x, n) 

nextafter(x) 

rint(x) 

sign(x) 
sign(x) 

spacing(x) 

signbit(x) 

trunc(x) 
trunc(x) 
trunc(x) 
Miscellaneous  
abs(x) 
abs(x) 
abs(x) 
clip(x, a, b) 

divmod(x, y) 

factorial(n) 

fmod(x, y) 
fmod(x, y) 

gcd(a, b) 
gcd(a, b) 

maximum(x, y) 

minimum(x, y) 

modf(x) 
modf(x) 

Mathematical constants  
e 
e 
e 
golden 

inf 
inf 
inf 
nan 
nan 
nan 
pi 
pi 
pi 
tau 
tau 
Trigonometric/hyperbolic functions¶

sin
(x)¶ Compute the trigonometric sine of angle
x
measured in radians.This function can only be applied to numeric columns (real, integer, or boolean), and produces a float64 result, except when the argument
x
is float32, in which case the result is float32 as well.

cos
(x)¶ Compute the trigonometric cosine of angle
x
measured in radians.This function can only be applied to numeric columns (real, integer, or boolean), and produces a float64 result, except when the argument
x
is float32, in which case the result is float32 as well.

tan
(x)¶ Compute the trigonometric tangent of
x
, which is the ratiosin(x)/cos(x)
.This function can only be applied to numeric columns (real, integer, or boolean), and produces a float64 result, except when the argument
x
is float32, in which case the result is float32 as well.

arcsin
(x)¶ The inverse trigonometric sine of
x
. In mathematics, this may also be written as \(\sin^{1}x\). This function satisfies the property thatsin(arcsin(x)) == x
for allx
in the interval[1, 1]
.For the values of
x
that are greater than 1 in magnitude, the function arcsine produces NA values.

arccos
(x)¶ The inverse trigonometric cosine of
x
. In mathematics, this may also be written as \(\cos^{1}x\). This function satisfies the property thatcos(arccos(x)) == x
for allx
in the interval[1, 1]
.For the values of
x
that are greater than 1 in magnitude, the function arcsine produces NA values.

arctan
(x)¶ The inverse trigonometric tangent of
x
. This function satisfies the property thattan(arctan(x)) == x
.

arctan2
(y, x)¶ The inverse trigonometric tangent of
y/x
, taking into account the signs ofx
andy
to produce the correct result.If
(x,y)
is a point in a Cartesian plane, thenarctan2(y, x)
returns the radian measure of an angle formed by 2 rays: one starting at the origin and passing through point(0,1)
, and the other starting at the origin and passing through point(x,y)
. The angle is assumed positive if the rotation from the first ray to the second occurs counterclockwise, and negative otherwise.As a special case,
arctan2(0, 0) == 0
, andarctan2(0, 1) == tau/2
..

sinh
(x)¶ The hyperbolic sine of
x
, defined as \(\sinh(x) = \frac12(e^x  e^{x})\).

cosh
(x)¶ The hyperbolic cosine of
x
, defined as \(\cosh(x) = \frac12(e^x + e^{x})\).

tanh
(x)¶ The hyperbolic tangent of
x
, defines as \(\tanh(x) = \frac{\sinh x}{\cosh x} = \frac{e^xe^{x}}{e^x+e^{x}}\).

arsinh
(x)¶ The inverse hyperbolic sine of
x
. This function satisfies the property thatsinh(arcsinh(x)) == x
. Alternatively, this function can also be computed as \(\sinh^{1}(x) = \ln(x + \sqrt{x^2 + 1})\).

arcosh
(x)¶ The inverse hyperbolic cosine of
x
. This function satisfies the property thatcosh(arccosh(x)) == x
. Alternatively, this function can also be computed as \(\cosh^{1}(x) = \ln(x + \sqrt{x^2  1})\).

artanh
(x)¶ The inverse hyperbolic tangent of
x
. This function satisfies the property thatsinh(arcsinh(x)) == x
. Alternatively, this function can also be computed as \(\tanh^{1}(x) = \frac12\ln\frac{1+x}{1x}\).

hypot
(x, y)¶ The length of a hypotenuse in a right triangle with sides
x
andy
, i.e. \(\operatorname{hypot}(x, y) = \sqrt{x^2 + y^2}\).

deg2rad
(x)¶ Convert an angle measured in degrees into radians: \(\operatorname{deg2rad}(x) = x\cdot\frac{\tau}{360}\).

rad2deg
(x)¶ Convert an angle measured in radians into degrees: \(\operatorname{rad2deg}(x) = x\cdot\frac{360}{\tau}\).
Exponential/logarithmic functions¶

exp2
(x)¶ Two raised to the power
x
.

expm1
(x)¶ Computes \(e^x  1\), however offering a better precision than
exp(x)  1
for small values ofx
.

log
(x)¶ The natural logarithm of
x
. This function is the inverse ofexp(x)
:exp(log(x)) == x
.

log10
(x)¶ The base10 logarithm of
x
, also denoted as \(\lg(x)\) in mathematics. This function is the inverse ofpower(10, x)
.

log1p
(x)¶ The natural logarithm of 1 plus
x
, i.e. \(\ln(1 + x)\).

log2
(x)¶ The base2 logarithm of
x
, this function is the inverse ofexp2(x)
.

cbrt
(x)¶ Compute the cubic root of
x
, i.e. \(\sqrt[3]{x}\).

power
(x, a)¶ Raise
x
to the powera
, i.e. calculate \(x^a\).

sqrt
(x)¶ The square root of
x
, i.e. \(\sqrt{x}\).

square
(x)¶ The square of
x
, i.e. \(x^2\).
Special mathemetical functions¶

erf
(x)¶ The error function \(\operatorname{erf}(x)\).
This function is defined as the integral \(\operatorname{erf}(x) = \frac{2}{\sqrt{\pi}} \int^x_0 e^{t^2}dt\). This function is used in computing probabilities arising from the normal distribution.

erfc
(x)¶ The complementary error function \(\operatorname{erfc}(x) = 1  \operatorname{erf}(x)\).
This function is defined as the integral \(\operatorname{erfc}(x) = \frac{2}{\sqrt{\pi}} \int^{\infty}_x e^{t^2}dt\).
For large values of
x
this function computes the result much more precisely than1  erf(x)
.

gamma
(x)¶ Euler gamma function of
x
.The gamma function is defined for all
x
except for the negative integers. For positivex
it can be computed via the integral \(\Gamma(x) = \int_0^\infty t^{x1}e^{t}dt\). For negativex
it can be computed as \(\Gamma(x) = \frac{\Gamma(x + k)}{x(x+1)\cdot...\cdot(x+k1)}\), where \(k\) is any integer such that \(x+k\) is positive.If x is a positive integer, then \(\Gamma(x) = (x  1)!\).

lgamma
(x)¶ Natural logarithm of the absolute value of gamma function of
x
.
Floatingpoint functions¶

isna
(x)¶ Returns True if
x
is an NA value, and False otherwise. If
x
is aFrame
, the function is applied separately to each element in the frame. The result is a new Frame where all columns are boolean, and with the same shape asx
. Each element in this new frame is a boolean indicator of whether the corresponding element inx
is an NA value or not.  If
x
is a columnexpression, thenisna(x)
is also an expression. The argument columnx
can be of any stype, and the result is a column with stype bool8. When evaluated withinDT[i, j, ...]
, the expressionisna(x)
produces a column where each element is an indicator of whether the corresponding value inx
is NA or not.  When
x
is a python integer,isna(x)
returns False.  When
x
is a python float,isna(x)
returns False for all values ofx
except for the floatnan
value. isna(None)
produces True.
 If

isfinite
(x)¶ Returns True if
x
is a finite value, and False ifx
is a positive/negative infinity of NA.

isinf
(x)¶ Returns True if
x
is a positive or negative infinity, and False otherwise.
Miscellaneous functions¶

abs
(x)¶ Return the absolute value of
x
. This function can only be applied to numeric arguments (i.e. boolean, integer, or real).The argument
x
can be one of the following: a
Frame
, in which case the function is applied to all elements of the frame, and returns a new frame with the same shape and stypes asx
. An error will be raised if any columns inx
are not numeric.  a columnexpression, in which case
abs(x)
is also a columnexpression that, when applied to some frameDT
, will evaluate to a column with the absolute values ofx
. The stype of the resulting column will be the same as the stype ofx
.  an
int
, or afloat
, in which caseabs(x)
returns the absolute value of that number, similar to the python builtin functionabs()
.
Examples:
DT = dt.Frame(A=[3, 2, 4, 17, 0]) DT[:, abs(f.A)]
C0 ▪ 0 3 1 2 2 4 3 17 4 0 See also
fabs()
 a
Mathematical constants¶

e
¶ The base of the natural logarithm, also known as the Euler’s number. Its value is
2.718281828459045
.

golden
¶ The golden ratio \(\varphi = (1 + \sqrt{5})/2\). The value is
1.618033988749895
.

inf
¶ Positive infinity.

nan
¶ Notanumber, a special floatingpoint constant that denotes a missing number. In most
datatable
functions you can useNone
instead ofnan
.

pi
¶ Mathematical constant \(\pi = \frac12\tau\), the area of a circle with unit radius. The constant is stored with float64 precision, and its value is
3.141592653589793
.

tau
¶ Mathematical constant \(\tau = 2\pi\), the circumference of a circle with unit radius. Some mathematicians believe that \(\tau\) is the true circle constant, and \(\pi\) is an impostor. The value of \(\tau\) is
6.283185307179586
.