Valid expressions for the Expression Editor

Expression Editor valid expressions

Expression Editor valid expressions

The following are valid:

• global parameters

• real and integer constants

• the label PI which is taken to be an approximation to π

• the arithmetic operations +, -, *, / and for raising to a power ^ or **

• the boolean operations: !, !=, &&, ||, >, <, >=, <=,= =

• parentheses "(" and ")" with their usual mathematical significance

• comma "," for separating variables

• The following functions of one variable:

abs

absolute value

exp

exponential

acos

arc cosine

fabs

absolute value of floating

acosh

inverse hyperbolic cosine

integ

integration

asin

arc sine

log

natural logarithm

asinsh

inverse hyperbolic sine

log10

base-10 logarithm

atan

arc tangent

sin

sine

atanh

inverse hyperbolic tangent

sinh

hyperbolic sine

cos

cosine

sqrt

square root

cosh

hyperbolic cosine

tan

tangent

differ

differentiation

tanh

hyperbolic tangent

• The following functions of two variables:

atan2

arc tangent of y/x

sign

sign

lsqrta

square root

• The following functions of two or more variables:

min

minimum

max

maximum

The meaning of most of these functions is obvious. However, here we give more details on some of them.

• atan: the function atan2(a,b) means atan(a/b) unless b=0 in which case it means atan( ) = π*/2* if and is an error otherwise.

• sign: the function sign(a,b) means the absolute value of a with the sign of b.

• differ: the function differ differentiates the argument with respect to time whereas integ integrates it. Note these two functions operate on the data stored in the results file. There is no control on error for these two functions and they should be regarded as rough estimates (1st order only).

• Isqrta: this utility is used to compute the square root of an input. The validity interval of the function lsqrta is . In fact, negative input values are accepted and the returned value is then .The function lsqrta also includes a linear region for input values which are too close to zero. The amplitude of this linear region centred on 0 can be set by the user with the xcrit. Then, for the square root is considered as linear. The slope of the linear part is adjusted to allow continuity between linear and non linear signals. Its value is . Figure 92: The characteristics of the function lsqrta

• max/min: returns the maximum or minimum of the arguments. You can enter as many arguments as you need.

Component Customization will check your expression. If it finds it acceptable, it will enter the expression as a value of a parameter if you started the Expression Editor from the value field of a parameter or variable.