Chapter 12Appendix: Formula Functions

This appendix lists all operators, constants, and functions you can use in formulas (Chapter 7). The values in the "Example" columns are results calculated with the sample data sample_endurance_run_en.csv (0–599.9 s, every 0.1 s, 6000 points).

12.1Syntax rules

• Write function names in lowercase. SIN(x) gives an unknown function error.
• The constants PI and E are uppercase. If you write pi, it is looked up as a series name.
• The following full-width and Japanese symbols are read as their half-width equivalents (not inside names enclosed in backquotes).

12.2Operators

• The order of evaluation is exponentiation → negation → multiplication and division → addition and subtraction.
• Exponentiation is evaluated from right to left. 2^3^2 is 2^9, which is 512.
• Negation comes after exponentiation. -2^2 is −(2^2), which is −4, and (-2)^2 is 4. Versions before 1.0.11 calculated -2^2 as 4. If a saved formula has this form, a notice appears when you open LOGADEC (formulas that use movavg are notified in the same way that the calculation rules changed).
• There is no remainder operator (%). It gives an invalid character error.

12.3Constants and variables

An expression that references no series (for example, sin(2*PI*x/60)) is calculated on the X of the data loaded on the screen. The status display shows "Ready (constants/functions only …)". It cannot be saved before data is loaded.

12.4Point-by-point functions

Calculated at each point. Arguments can be series, numbers, or expressions.

• Points that cannot be calculated have no value (NaN). Examples: sqrt(-1), log(-1), 1/0. The graph line breaks there.
• min and max compare point by point. For the minimum and maximum of a whole series, use minval and maxval. Example: max(`Current`, 15) sets points below 15 A to 15.

12.5Aggregate functions

Calculates one value from the whole series and puts the same value at every point. Write one series or expression as the argument.

• Points without a value are excluded from the calculation.
• With X range, only points within the range are used.
• The argument can be an expression. mean(`Current`*2) is 34.648. sum(1) gives the number of points (6000).
• Common forms: `Oil temp` - mean(`Oil temp`) (deviation from the mean), `Vibration RMS` / maxval(`Vibration RMS`) (normalize the maximum to 1).

12.6Time-series functions

Calculated using the points before and after.

diff

• The unit is "the unit of the original series ÷ the X unit". If X is in seconds, it is the change per second.
• The first point has no value because there is no previous point.
• Points where X does not increase (the same time or a time going backward), and points where the point before or after has no value, have no value.

integ

• The unit is "the unit of the original series × the X unit". Integrating power (W) over seconds gives J. To get Wh, divide by 3600.
• The first point is 0.
• The following intervals are not added (the integral stays as it is and continues adding from the next interval).
• Intervals where either end has no value
• Intervals where the X spacing exceeds 1.5 times the step (the median interval)
• Intervals where X does not increase

movavg

• n is an integer of 1 or more, written as a number (series and decimals cannot be used). If omitted, it is 5.
• The first n−1 points have no value because not enough points are available.
• If any of the n points being averaged has no value, that point also has no value.
• Example: movavg(`Current`) is a 5-point average; the value at 0.4 s is 14.0486, the mean of the 5 points from 0 to 0.4 s.

shift

• n is an integer, written as a number. If omitted, it is 1.
• Points that fall outside the data as a result of shifting have no value.
• Example: `Speed` - shift(`Speed`, 1) is the difference from the adjacent point.

12.7Error messages

If the expression has an error, the reason appears in the status display, and the formula cannot be saved.