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# Functions for defining parameters

Like variables, the parameter functions are split into function groups.

### Time

Functions in this group all return a time, either in seconds or normalized to percent if you specify the Time Normalize Between events.

• Event A. The time of A.
• Event A to Event B. The duration from A to B.
• Variable A max value [Event A, Event B]. The time when variable A attains its maximum value between two events of type A and B.
• Variable A min value [Event A, Event B]. As above, but for the minimum value.
• Variable A crossing Value going up [Event A, Event B]. The time of variable A crossing a Threshold value on the way up, between two events of type A and B.
• Variable A crossing Value going down [Event A, Event B]. As above, but crossing the threshold going down.

### Total time

These functions calculate the total time a variable fulfils a certain condition.

• Above Value [Event A, Event B]. The total time a variable is above a certain threshold value, in seconds, between events A and B.
• Below Value [Event A, Event B]. As above, but the time the variable is below the threshold value.

### Frequency

This group contains only one function.

• [Event A, Event B], this calculates how often the event pair A and B occurs. This could, for example, be used to calculate cadence, which is the step frequency, by specifying event A as foot strike and B as foot off. Although the standard unit for frequency is Hz, you can also choose units such as steps/min.

### Value

These functions calculate the value of a variable, or the value of a combination of variables, at specific points in time.

• Variable A [Event A]. Simply the value of the variable at the time specified by the event.
• Variable A [Event A] + Variable B [Event B]. The two variable values added together, the values taken at the points in time specified by events A and B, respectively.
• Variable A [Event A] –Variable B [Event B]. Variable B subtracted from A.
• Variable A range [Event A, Event B]. Variable A’s range (that is, its minimum value subtracted from its maximum value) for the time span defined by events A and B.
• Variable A max [Event A, Event B]. Variable A’s maximum value for the time span defined by events A and B.
• Variable A min [Event A, Event B]. As above, except for Variable A’s minimum value.

### Integrated

This group contains only one function.

• Variable A [Event A, Event B], calculates the integral over the time span defined by events A and B.

### RMS

This stands for “root mean square”, which adds up the square of all sample points and finally returns the square root of the sum.

• Variable A [Event A, Event B]. Calculates the RMS of variable A between the events A and B.
• Variable A –Variable B [Event A, Event B]. Calculates the RMS of the difference between variables A and B over the time span defined by events A and B.

### Average

These functions calculate the average value of a variable, or a combination of variables.

• Variable A [Event A, Event B]. The average of each sample point over the time span defined by events A and B.
• Variable A’s local coordinates in Variable B [Event A, Event B]. Variable A can be either a point or a segment, whereas variable B has to be a segment. The function calculates the average position (and, if a segment, orientation) of A in B’s reference frame. The main use of this function is to store an anatomical point or segment in a technical segment’s reference system based on a static trial, which can be used later in a dynamic trial.

### Stdev

Equivalent to the average function above, except that it calculates the standard deviation.

• Only Variable A [Event A, Event B] is available.

### 3D

Functions in this group calculate parameters based on 3D variables.

• Distance Variable A [Event A] to Variable B [Event B]. Calculates the straight-line distance from the 3D variable A to the 3D variable B.
• Speed Variable A [Event A, Event B]. Calculates the speed of 3D variable A between event A and event B. This corresponds to the distance covered divided by the time between the two events.
• Distance Travelled Variable A [Event A, Event B]. Calculates the 3D distance traveled by variable A between events A and B. This is calculated by adding each line segment traveled for each frame between the two events.

### Temporal

These are special functions for calculating typical temporal parameters.

• Single Support [Event A, Event B] – [Event C, Event D]. Calculates the time between events A and B, but then subtracts the time outside the span defined by event C to event D, should either of these lie inside the A to B span. When A = ipsilateral foot contact, B = ipsilateral foot off, C = contralateral foot off and D = contralateral foot contact, single support is calculated as the total stance time (A to B) minus the time of double support (A to C and D to B). However, should C and D lie outside the span A to B (for example when a running motion is analyzed), nothing is subtracted since there is no double support.
• Double Support [Event A, Event B] – [Event C, Event D]. Calculates the time from event A to event B minus the time inside the span defined by event C to event D.

### Parameter

These functions enable you to combine other parameters.

• Parameter A + Parameter B. Adds two parameters.
• Parameter A –Parameter B. Subtracts parameter B from parameter A.
• Parameter A * Parameter B. Multiplies the two parameters.
• Parameter A / Parameter B. Divides parameter A with B.
• (Parameter A + Parameter B) / 2. Takes the average of two parameters.