--- title: "Functions for defining parameters" canonical: "https://help.vicon.com/space/ProCalc16/12651106/Functions%20for%20defining%20parameters" format: markdown --- Like variables, the parameter functions are split into function groups. > Macro (toc) ### 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.