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Scilab Help >> Xcos > palettes > User defined functions palette > EXPRESSION

EXPRESSION

Mathematical expression

Block Screenshot

Description

The Expression block applies the specified Scilab expressions to its input.

Parameters

  • number of inputs

    Block input can be a scalar or vector.

    Properties : Type 'vec' of size 1

  • scilab expression

    The Scilab expression applied to the input.

    Properties : Type 'vec' of size 1

    All Scilab operators are supported.

    Only a restricted list of functions are supported in the expression.

    Name#rhs
    sin 1
    cos 1
    tan 1
    asin 1
    acos 1
    atan 1
    atan2 2
    Name #rhs
    sinh 1
    cosh 1
    tanh 1
    asinh 1
    acosh 1
    atanh 1
    Name#rhs
    exp 1
    log 1
    log10 1
    int 1
    round 1
    ceil 1
    floor 1
    Name#rhs
    sign 1
    abs 1
    min 2
    max 2

    In the provided expression, any subexpression being an exponent more than 1-character long must end with a space, to be correctly displayed on the block's icon.

    This constrain has no consequence on the computational validity of the expression.

    Examples: "u1^12-u2", "u1^ 12-u2", "u1^abc - 3", "u1^(u2-3) + 4" will be correctly displayed, while "u1^abc-3" would be displayed as "u1^{abc-3}" (but well computed as u1^abc + 3) and "u1^(u2-3)+4" as "u1^{(u2-3)+4}" instead of "u1^{(u2-3)} + 4". "u1^abc - 3" and "u1^(u2-3) + 4" will have to be entered instead.
  • use zero-crossing

    Select to enable zero crossing detection.

    Properties : Type 'vec' of size 1

Default properties

  • always active: no

  • direct-feedthrough: yes

  • zero-crossing: yes

  • mode: yes

  • regular inputs:

    - port 1 : size [1,1] / type 1

    - port 2 : size [1,1] / type 1

  • regular outputs:

    - port 1 : size [1,1] / type 1

  • number/sizes of activation inputs: 0

  • number/sizes of activation outputs: 0

  • continuous-time state: no

  • discrete-time state: no

  • object discrete-time state: no

  • name of computational function: evaluate_expr

Example

The following example calculate an arbitrary expression with multiple different configuration or blocks.

y = u(1) - u(2) - u(3)

Interfacing function

  • SCI/modules/scicos_blocks/macros/Misc/EXPRESSION.sci

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Last updated:
Tue Feb 25 08:49:22 CET 2020