Formulas

The formula syntax below can be used to add calculated variables when loading data:

In the upload screen in Njord Player or Njord Analytics
In Njord Analytics, modify already uploaded data by selecting the uploaded data segment (Data section), and select Process
In Njord Analytics, configure one or more formulas to be applied every time data is uploaded to a certain boat. Set this up under Boat - Settings - Process

Examples

Formula	Description
`Heading - COG`	Difference between `Heading` and `COG`
`DELTAPERSEC(UNWRAP(Heading))`	Rate of turn in degrees per second
`DELTAPERSEC(BoatSpeed) * 60`	Acceleration in knots per minute
`BoatSpeed / -(FILTER(DELTASEC(BoatSpeed, 10), DELTASEC(BoatSpeed, 10) < 0) / 10)`	When decelerating, how many seconds to zero knots at current 10 second deceleration average
`INTERPOLATED(SERIES("2022-10-01T08:00+02:00", 10, "2022-10-01T11:00+02:00", 14))`	This could be `TWS` rising from 10 kts at 8 am to 14 kts at 11 am, for example

Operators

Operator	Description	Notes
`+`	Addition
`-`	Subtraction
`*`	Multiplication
`/`	Division
`<`	Less than	To be used with `FILTER()`
`<=`	Less than equal	To be used with `FILTER()`
`>`	Greater than	To be used with `FILTER()`
`>=`	Greater than equal	To be used with `FILTER()`
`==`	Equals	To be used with `FILTER()`
`!=`	Not equals	To be used with `FILTER()`
`&`	Logical and	To be used with `FILTER()`
\|	Logical or	To be used with `FILTER()`
`!`	Negate	To be used with `FILTER()`

Functions

Function	Description
`ABS(value)`	Absolute of value / remove sign
`MIN(value1, value2)`	Minimum of two values
`MAX(value1, value2)`	Maximum of two values
`MOD(a, n)`	Modulo operation
`SIN(value)`	Sine of `value` (which is expected to be in degrees)
`COS(value)`	Cosine of `value` (which is expected to be in degrees)
`ARCTAN2(x, y)`	Element-wise arc tangent (in degrees) of `x`/`y` choosing the quadrant correctly.
`FILTERPORT(value)`	Retains the value only on port tack (`AWA` between -170 and -10)
`FILTERSTBD(value)`	Retains the value only on starboard tack (`AWA` between 10 and 170)
`COALESCE(value1, value2)`	Choose `value1` if it's not empty, else `value2`
`SELECTPORTSTBD(valuePort, valueStbd)`	Select `valuePort` when sailing on port tack, `valueStbd` on starboard tack
`UNWRAP(value)`	Removes wrap at 0/360 degrees, instead expands value below 0 or above 360 as needed for safe calculations
`SHIFT(value, rows)`	Shifts value (series) by given number of rows
`SHIFTSEC(value, seconds)`	Shifts value (series) by given number of seconds
`DELTASEC(value, seconds)`	Delta of value compared to `second` seconds ago
`DELTAPERSEC(value)`	Delta of value compared to previous datapoint, divided by number of seconds since last datapoint
`ROLLINGMEAN(value, seconds)`	Rolling mean over `second` seconds
`ROLLINGSUM(value, seconds)`	Rolling sum over `second` seconds
`FILTER(value, mask)`	Filters value using the given mask, returning empty value where the mask is false
`INTERPOLATED(value)`	Fill blanks between values by linear interpolation
`INTERPOLATEDBEARING(value)`	Fill blanks between values by linear interpolation, correctly handling 0/360 degree wrap around
`SERIES(time1, value1, time2, value2, ...)`	Produces a data series with the given values at the given times. Write times in ISO 8601 format with quotes, like `"2022-10-01T10:00+02:00"`. Use with `INTERPOLATED()`.
`TWA(awa, aws, sog)`	Calculates true wind angle from apparent wind and SOG/boat speed
`TWS(awa, aws, sog)`	Calculates true wind speed from apparent wind and SOG/boat speed
`AWA(twa, tws, sog)`	Calculates apparent wind angle from true wind and SOG/boat speed
`AWS(twa, tws, sog)`	Calculates apparent wind speed from true wind and SOG/boat speed
`INTEGRATE(value, gap)`	Integration over time (in seconds) using the trapezoidal rule. `gap` is optional (defaults to 10 seconds) - any gaps in data greater than this are omitted.

Note: all function names are case insensitive and may be written in lower case too.