DDFN Tommorow - Today = Todays Flow

Calculates the difference between today's value and tomorrow's value for an existing variable, VX.

SYNTAX:

DDFN(Vx, Optional Rollover)

NOTES:

If the next day's value is not present, the program searches up to 7 days to find the next value for VX to determine the difference. If no future entry is found within 7 days, no calculation will be done. The optional Rollover specifies the Rollover point.  If the optional parameter is not specified, the system assumes the rollover point is at the next power of 10. The system assumes rollover occurs if tomorrow's value is less than today's value and makes the appropriate entry. This function should be used when data collected on one day requires the next day's data for calculation.

A day is defined as 7:00 a.m. to 7:00 a.m. The meter for influent flow (V1) is read every day at 7:00 a.m. In order to get the flow for today, the difference between today's reading and tomorrow's reading must be calculated (Tommorow - Today = Today's Flow).

EXAMPLES:

Example 1:

V43 = DDFN(V41)

Calculates the daily difference of values stored in variable 41, and records them as variable 43. Consider the following example.

NOTE: No data will be calculated until an entry for the next day is recorded.

Example 2: 

V43 = DDFN(V42,990)

Calculates daily difference of values stored in variable 42, and records them as variable 44.  Meter rollsover at 990. Consider the following example illustrating rollover and lookback.

NOTE:  The DDFN function can be used with Daily Detail variables (Hourly, 15 minute...) to calculate a daily result.  The DDFN function will use the first Daily Detail reading found for tomorrow minus the first Daily Detail reading found for the day.