# Complicated Functions in the widget settings

#### Complicated functions instead of simple Arithmetic operations

In the widget's settings, there is a section "Arithmetic operation". It seems easy for multiplied or divided by the coefficient and got the desired value, for example, divided Watts by 1000 and got Kilo-Watts. But among the arithmetic operations, there was a powerful tool **f(x)** with which you can describe any parameter based on the data that your smart meter monitors, for example, reactive energy in VAR, generated heat in Kilo-Watts or dew point in degrees Celsius. When calculating such indicators a simple arithmetic operation is not enough, usually, it is a formula and quite complicated.

This is where the **f(x)** tool comes to help in the "Arithmetic operation" settings, it is easier to use than it seems.

The main idea of the tool f (x): *you can write any complicated formula to get any new parameters using the parameters measured by the device and the JavaScript syntax.*

Use the parameters measured by the device to construct formulas, in the format below:

- d.W1 - Power for 1st line;
- d.V2 - Voltage for 2nd line;
- d.A3 - Current for 3rd line;
- and so on.

The list of available parameters is presented on the left side in the formula editing window.

*Important, the register of symbols matters!*

You also need to remember the rules of expression construction in mathematics and the order of calculation:

- Actions written in brackets;
- Multiplication and division;
- Addition and subtraction.

For complex calculations, there is the Math library, which will provide you with trigonometric functions, power, roots, and logarithms. Below is a list of the Math object, which includes mathematical constants and functions in its properties and methods.

- Math.floor(a) rounds to the next smallest integer;
- Math.abs(a) returns the absolute value of a;
- Math.pow(a, b) computes a to the power of b;
- Math.sqrt(a) computes the square root of a;
- Math.log(a) computes the natural logarithm of a;
- Math.sin(a) calculates the sine of angle a;
- Math.cos(a) computes the cosine of a;
- Math.tan(a) calculates the tangent of angle a;
- Math.asin(a) calculates arcsine of a;
- Math.acos(a) arccosine of a;
- Math.atan(a) arctangent of a;

There is also a list of useful constants.:

- Math.PI (PI): 3.141592653589793
- Math.SQRT2 (the square root of two): 1.4142135623730951
- Math.SQRT1_2 (half of the square root of two): 0.7071067811865476
- Math.E (e or Euler number): 2.718281828459045
- Math.LN2 (natural logarithm of 2): 0.6931471805599453
- Math.LN10 (natural logarithm of 10): 2.302585092994046
- Math.LOG2E (the binary logarithm of e): 1.4426950408889634
- Math.LOG10E (the decimal logarithm of e): 0.4342944819032518

To check the correctness of the calculations, use the "Check" button, which will perform the calculation with the listed parameter values.

For example, will build a “Dew Point” graph based on Temperature and Humidity, which can be easily measured using the smart-MAC D105.

The formula for finding the Dew Point is not so simple:

But in the widget settings, it looks not so scary.

(237.7 * ((17.27*d.T1)/(237.7 + d.T1) + Math.log(d.T2/100))) / (17.27 - ((17.27*d.T1)/(237.7+d.T1) + Math.log(d.T2/100)))

Where: d.T1 is the measured Temperature and d.T2 is the measured Relative Humidity.

### Successes in monitoring!

Customer support service by UserEcho

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