Creating New equation

[Nikospps]

Hello! I would like to create a new equation using a specific variable.

This variable shows the total energy every specific time (refresh every 5 sec). I aim to create an equation where will be done a subtraction between this variable at 00:00 of this day (subtracter) and the instant Value of energy (subtrahend) as i take it from Mango.

Let's assume E is the total energy variable, i would like to create an equation like: E(t)-E(00:00-start of the day). Is any way to implement this?

Thanks in advance,
Nikos.

[phildunlap]

Hi Nikos,

Yes, you could use a meta point like,

var dayStartTime = new Date();
dayStartTime.setHours(0);
dayStartTime.setMinutes(0);
dayStartTime.setSeconds(0);
dayStartTime.setMilliseconds(1);

//Get the value before the first millisecond of the day 
// (00:00:00.000, or the last value from yesterday if it didn't change)
var subtracter = variableContextPoint.pointValueBefore(dayStartTime.getTime())
var subtrahend = energyContextPoint.value;

if(subtracter == null)
  return -subtrahend;
return subtracter.doubleValue - subtrahend;