Chapter 7. Mathematical Expressions and Scripting
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## Chapter 7. Mathematical Expressions and Scripting

Starting with version 0.8.7, QtiPlot supports different interpreters for evaluating mathematical expressions and for executing scripts.

## muParser

The constants _e=e=E and _pi=pi=PI=Pi are defined, as well as the following operators and functions.

Table 7.1. Supported Mathematical Operators

Name | Description
--- | ---
+ | Addition
- | Substraction
* | Multiplication
/ | Division
^ | Exponentiation (raise a to the power of b)
and | logical and (returns 0 or 1)
or | logical or (returns 0 or 1)
xor | logical exclusive or (returns 0 or 1)
< | less then (returns 0 or 1)
<= | less then or equal (returns 0 or 1)
== | equal (returns 0 or 1)
>= | greater then or equal (returns 0 or 1)
> | greater then (returns 0 or 1)
!= | not equal (returns 0 or 1)

Table 7.2. Mathematical Functions

Name | Description
--- | ---
abs(x) | absolute value of x
acos(x) | inverse cosinus
acosh(x) | inverse hyperbolic cosinus
asin(x) | inverse sinus
asinh(x) | inverse hyperbolic sinus
atan(x) | inverse tangent
atanh(x) | inverse hyperbolic tangent
avg(x1,x2,x3,...) | average value, this command accept a list of arguments separated by commas
bessel_j0(x) | Regular cylindrical Bessel function of zeroth order, J0(x).
bessel_j1(x) | Regular cylindrical Bessel function of first order, J1(x).
bessel_jn(x,n) | Regular cylindrical Bessel function of nth order, Jn(x).
bessel_y0(x) | Irregular cylindrical Bessel function of zeroth order, Y0(x) for x>0.
bessel_y1(x) | Irregular cylindrical Bessel function of first order, Y1(x) for x>0.
bessel_yn(x,n) | Irregular cylindrical Bessel function of nth order, Yn(x) for x>0.
beta (a,b) | Computes the Beta Function, B(a,b) = Gamma(a)*Gamma(b)/Gamma(a+b) for a > 0 and b > 0.
cos(x) | cosinus of x
cosh(x) | hyperbolic cosinus of x
erf(x) | error function of x
erfc(x) | Complementary error function erfc(x) = 1 - erf(x).
erfz(x) | The Gaussian probability density function Z(x).
erfq(x) | The upper tail of the Gaussian probability function Q(x).
exp(x) | Exponential function: e raised to the power of x.
gamma(x) | Computes the Gamma function, subject to x not being a negative integer
gammaln(x) | Computes the logarithm of the Gamma function, subject to x not a being negative integer. For x<0, log(|Gamma(x)|) is returned.
hazard(x) | Computes the hazard function for the normal distribution h(x) = erfz(x)/erfq(x).
ln(x) | natural logarythm of x
log(x) | decimal logarythm of x
log2(x) | base 2 logarythm of x
min(x1,x2,x3,...) | Minimum of the list of arguments
max(x1,x2,x3,...) | Maximum of the list of arguments
rint(x) | Round to nearest integer.
sign(x) | Sign function: -1 if x<0; 1 if x>0.
sin(x) | sinus of x
sinh(x) | hyperblic sinus of x
sqrt(x) | square root of x
tan(x) | tangent of x
tanh(x) | hyperbolic tangent of x

Table 7.3. Non-Mathematical Functions

Name | Description
--- | ---
cell(a,b) | In the contex of a matrix, returns the value at row a and column b. In the context of a table, returns the value at column a and row b (remember that tables use column logic). Everywhere else, this function is undefined.
col(c) | Only works in the context of a table. Returns the value at column c and row i (the current row) in the context table. c can either be the column's number, or its name in doublequotes.
if(e1,e2,e3) | if e1 is true, e2 is executed else e3 is executed.
tablecol(t,c) | Only works in the context of a table. Returns the value at column c and row i (the current row) in the table t. t is the table's name in doublequotes, c is either the column's number or its name in doublequotes.

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