Functions

The functions in gnuplot are the same as the corresponding functions in the Unix math library, except that all functions accept integer, real, and complex arguments, unless otherwise noted.

For those functions that accept or return angles that may be given in either degrees or radians (sin(x), cos(x), tan(x), asin(x), acos(x), atan(x), atan2(x) and arg(z)), the unit may be selected by set angles, which defaults to radians.

Math library functions
Function	Arguments	Returns
abs(x)	any	absolute value of 10#10, 11#11; same type
abs(x)	complex	length of 10#10, 12#12
acos(x)	any	13#13 (inverse cosine)
acosh(x)	any	14#14 (inverse hyperbolic cosine) in radians
arg(x)	complex	the phase of 10#10
asin(x)	any	15#15 (inverse sin)
asinh(x)	any	16#16 (inverse hyperbolic sin) in radians
atan(x)	any	17#17 (inverse tangent)
atan2(y,x)	int or real	18#18 (inverse tangent)
atanh(x)	any	19#19 (inverse hyperbolic tangent) in radians
EllipticK(k)	real k 20#20 (-1:1)	21#21 complete elliptic integral of the first kind
EllipticE(k)	real k 20#20 [-1:1]	22#22 complete elliptic integral of the second kind
EllipticPi(n,k)	real n4#41, real k 20#20 (-1:1)	23#23 complete elliptic integral of the third kind
besj0(x)	int or real	24#24 Bessel function of 10#10, in radians
besj1(x)	int or real	25#25 Bessel function of 10#10, in radians
besy0(x)	int or real	26#26 Bessel function of 10#10, in radians
besy1(x)	int or real	27#27 Bessel function of 10#10, in radians
ceil(x)	any	28#28, smallest integer not less than 10#10 (real part)
cos(x)	any	29#29, cosine of 10#10
cosh(x)	any	30#30, hyperbolic cosine of 10#10 in radians
erf(x)	any	31#31, error function of real(10#10)
erfc(x)	any	32#32, 1.0 - error function of real(10#10)
exp(x)	any	33#33, exponential function of 10#10
floor(x)	any	34#34, largest integer not greater than 10#10 (real part)
gamma(x)	any	35#35, gamma function of real(10#10)
ibeta(p,q,x)	any	36#36, ibeta function of real(37#37,38#38,10#10)
inverf(x)	any	inverse error function of real(10#10)
igamma(a,x)	any	39#39, igamma function of real(40#40,10#10)
imag(x)	complex	imaginary part of 10#10 as a real number
invnorm(x)	any	inverse normal distribution function of real(10#10)
int(x)	real	integer part of 10#10, truncated toward zero
lambertw(x)	real	Lambert W function
lgamma(x)	any	41#41, lgamma function of real(10#10)
log(x)	any	42#42, natural logarithm (base 43#43) of 10#10
log10(x)	any	44#44, logarithm (base 45#45) of 10#10
norm(x)	any	normal distribution (Gaussian) function of real(10#10)
rand(x)	any	46#46, pseudo random number generator
real(x)	any	real part of 10#10
sgn(x)	any	1 if 47#47, -1 if 48#48, 0 if 49#49. imag(10#10) ignored
sin(x)	any	50#50, sine of 10#10
sinh(x)	any	51#51, hyperbolic sine of 10#10 in radians
sqrt(x)	any	52#52, square root of 10#10
tan(x)	any	53#53, tangent of 10#10
tanh(x)	any	54#54, hyperbolic tangent of 10#10 in radians

String functions
Function	Arguments	Returns
gprintf("format",x)	any	string result from applying gnuplot's format parser
sprintf("format",x,...)	multiple	string result from C-language sprintf
strlen("string")	string	int length of string
strstrt("string","key")	strings	int index of first character of substring "key"
substr("string",beg,end)	multiple	string "string"[beg:end]
strftime("timeformat",t)	any	string result from applying gnuplot's time parser
strptime("timeformat",s)	string	seconds since year 2000 as given in string s
system("command")	string	string containing output stream of shell command
word("string",n)	string, int	returns the nth word in "string"
words("string")	string	returns the number of words in "string"

other gnuplot functions
Function	Arguments	Returns
column(x)	int	column 10#10 during datafile manipulation.
defined(X)	variable name	[DEPRECATED] returns 1 if X is defined, 0 otherwise.
exists("X")	"variable name"	returns 1 if a variable named X is defined, 0 otherwise.
stringcolumn(x)	int	content of column 10#10 as a string.
timecolumn(x)	int	timecolumn 10#10 during datafile manipulation.
tm_hour(x)	int	the hour
tm_mday(x)	int	the day of the month
tm_min(x)	int	the minute
tm_mon(x)	int	the month
tm_sec(x)	int	the second
tm_wday(x)	int	the day of the week
tm_yday(x)	int	the day of the year
tm_year(x)	int	the year
valid(x)	int	test validity of 55#55 during datafile manip.