Expressions: Difference between revisions
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| pi() || 3.14159265358979323846 | | pi() || 3.14159265358979323846 | ||
|- | |- | ||
| | | gravity_vector() || gravity vector in the laboratory coordinate system. For a z-up coordinate system returns (0,0,-9.81) | ||
|- | |- | ||
| [[Expression Numbers#random|rand()]] || Generate a random number | | [[Expression Numbers#random|rand()]] || Generate a random number | ||
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:it works quite well, but there is one circumstance where this choice of delimiter is a nuisance. | :it works quite well, but there is one circumstance where this choice of delimiter is a nuisance. | ||
::and that is when you want & to actually be a logical and and the parser throws it away | ::and that is when you want & to actually be a logical and and the parser throws it away | ||
:: in this case you can use the reserved string AMP | |||
:: it was only really ugly before version 2024_04 because it didn't work before then | |||
: | |||
:Example given a file that has TAGS labelled TEST1 and TEST2 | |||
:To select files containing the tags TEST1 and TEST2 | |||
::Select_Active_File | ::Select_Active_File | ||
:: /FILE_NAME=ALL_FILES | ::/FILE_NAME=ALL_FILES | ||
:: /QUERY=TEST1 | ::/QUERY=TEST1 & TEST2 | ||
::! /SUBJECT_TAGS=NO_SUBJECT | ::! /SUBJECT_TAGS=NO_SUBJECT | ||
::''';''' | ::''';''' | ||
:: | ::! But what if you want to generalize and use another pipeline parameter for TEST2 | ||
::Set_Pipeline_Parameter | |||
::/PARAMETER_NAME=SCOTT2 | |||
::/PARAMETER_VALUE=TEST1 &::AMP &::SCOTT | |||
::''';''' | |||
::Select_Active_File | |||
::/FILE_NAME=ALL_FILES | |||
::/QUERY=TEST1 &::AMP &::SCOTT | |||
::! /SUBJECT_TAGS=NO_SUBJECT | |||
::''';''' | |||
===[[Brackets|Brackets]]=== | ===[[Brackets|Brackets]]=== |
Latest revision as of 20:35, 3 June 2024
Language: | English • français • italiano • português • español |
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Many (but not all) edit boxes and pipeline command parameters allow the use of expressions instead of numerical values. Visual3D uses a common expression parser, so the following syntax is common across all command parameters that allow expressions.
Evaluate_Expression Command
The Evaluate_Expression command allows the users to include expressions for defining the processing of the signals.
- Evaluate_Expression
- /Expression=
- !/Signal_Type=
- !/Signal_Folder=
- !/Signal_Name=
- /Result_Type=
- /Result_Folder=
- /Result_Name=
- !/Apply_as_suffix_to_signal_name=FALSE
- ;
Expression_Items
- Data Tree Signals
- Expressions_in_Model_Builder_Mode
- Pipeline_Parameters
- Tags
- C3D_Parameters
- Model Metrics
- String Data
Visual3D Reserved Characters
There are five characters that cause the equation parser considerable trouble. We have introduced reserved pipeline commands that can be used in the place of these characters.
Visual3D Reserved Names
Reserved_Names CURRENT_SIGNAL short hand for signal names NAN Not a Number isNAN Is Not a Number?
Numbers
Mathematical Constants pi() 3.14159265358979323846 gravity_vector() gravity vector in the laboratory coordinate system. For a z-up coordinate system returns (0,0,-9.81) rand() Generate a random number
Mathematical Operators
- Note: Visual3D parses the mathematical operators before it parses the signal names. If you have a signal name that contains a mathematical operator (e.g. R-Foot1), Visual3D will probably not be able to parse the equation expression properly.
- Also Note the potential conflict between some of the operators and the reserved characters. If the string is obviously an expression, there is no conflict.
Mathematical Operators + Plus or Add - Minus or Subtract * Multiply / Divide ^ Power -> for example, x^2 = x to the power 2 | logical OR -> the adjective NOT is allowed & logical AND -> the adjective NOT is allowed == OR = Equals <> OR >< Not Equals < Less Than <= OR =< Less Than or Equals To > Greater Than >= OR => Greater Than or Equals To NOT() NOT()
The ugly truth of the logical and
- & is used by Visual3D for concatenating strings
- it works quite well, but there is one circumstance where this choice of delimiter is a nuisance.
- and that is when you want & to actually be a logical and and the parser throws it away
- in this case you can use the reserved string AMP
- it was only really ugly before version 2024_04 because it didn't work before then
- Example given a file that has TAGS labelled TEST1 and TEST2
- To select files containing the tags TEST1 and TEST2
- Select_Active_File
- /FILE_NAME=ALL_FILES
- /QUERY=TEST1 & TEST2
- ! /SUBJECT_TAGS=NO_SUBJECT
- ;
- ! But what if you want to generalize and use another pipeline parameter for TEST2
- Set_Pipeline_Parameter
- /PARAMETER_NAME=SCOTT2
- /PARAMETER_VALUE=TEST1 &::AMP &::SCOTT
- ;
- Select_Active_File
- /FILE_NAME=ALL_FILES
- /QUERY=TEST1 &::AMP &::SCOTT
- ! /SUBJECT_TAGS=NO_SUBJECT
- ;
Brackets
Functions
- Visual3D has pre-defined functions imbedded in the pipeline to help you out.
- These functions are commonly used or have been added based on customer use.
Metric Functions
Signal Functions
String Data
Least Squares Fitting of Data
Intersection Functions
Assigned Force Functions
Trigonometric Functions
Array and Matrix Functions
Common Math Expressions
- int(a) - truncate each component to the nearest integer
- round(a) - round each component to the nearest integer
- fmod(y,x) - Returns the floating-point remainder of y/x
- => y and x must be one dimensional signals; returns a one dimensional signal
- abs(a) - absolute value
- sign(a)= sign of the signal ((a<0)=-1, (a>0)=1, (a==0) = 0
- sqrt(a) - square root
- exp(a) - exponent
- log(a) - natural log
- log10(a) - log base 10
- length(x) -- creates the length (magnitude) of a vector
- distance(a,b) -- distance between two signals.
- Example
- Evaluate_Expression
- /Expression= distance(LANDMARK::ORIGINAL::RIGHT_HIP , TARGET::ORIGINAL::LHIP)
- /Result_Name=PROX_THIGH_RADIUS
- ! /Result_Type=DERIVED
- ! /Result_Folder=PROCESSED
- ;
- dot (a, b) -- creates the dot product of a and b
- cross (a, b) -- creates the cross product of a and b
- NOTE: Often you will want to do dot (a, b)/ length (b), or cross (a, b) / length (b)
Expression Examples
Examples of using Evaluate_Expressions can be found here: Expressions Examples