Starting FSQM v2.5.2, we have included a Mathematical Evaluator element using which you can calculate complex formula on the go. Here is a live example of what it would look like.
To get started, please read on.
#1: Using numerical elements:
We two options for numerical calculations. One is to assign numeric value to existing element options, while the other is to use a numerical type element.
#1.1: Assign Numeric Values
Starting v2.5.2, numerical values can be added to the options of the following elements
- Multiple Choice Questions > Single Options
- Multiple Choice Questions > Multiple Options
- Multiple Choice Questions > Dropdown Options
- Other Form Elements > Radio Options
- Other Form Elements > Checkbox Options
- Other Form Elements > Dropdown Option
The value you assign on the option’s Numeric attribute will be used for the calculation.
#1.2: Using Numeric Elements
Following numeric elements are available.
- Multiple Choice Questions > Single Slider
- Multiple Choice Questions > Spinners
- Multiple Choice Questions > Multiple Grading – Slider Type
- Multiple Choice Questions > Star Rating
- Multiple Choice Questions > Scale Rating
- Feedback & Upload > Feedback Small Text
- Feedback & Upload > Mathematical Evaluator
- Other Form Elements > Small Text
- Other Form Elements > Keypad
- Other Form Elements > Single Checkbox
For these elements, either straight numeric values can be entered by the user or the option they choose has a numeric value (like ratings).
For toggle type elements (Toggle and Single Checkbox, under v2.5.4 only) if it is checked, then the value returned is 1, otherwise 0.
F1 :: M0+F2 and F2 :: M9+F1) would produce infinite loop on your browser.#2: Adding Mathematical Evaluator
Mathematical Evaluator can be found inside Feedback & Upload elements. Simply drag or click on the item to add it to a form container.
Here are the important settings:
- Value Editable By User: If enabled, then an input will be shown where user can edit the value.
- Decimal Precision: Number of digits after decimal points to which the value would be rounded.
- Prefix: HTML before value.
- Suffix: HTML after value.
#3: Mathematical Formula with Notations
The evaluator works on formula which you need to give. The formula can be any proper mathematical formula with special variables to fetch values from one of the supported fields. A sample formula would be (M10*M14)/(M15+M16).
#3.1: Variable Naming
The variable naming rule is as follows. The examples are explained with respect to the variable name M18R1.
| Position | Accepted Characters | No. of Character | Description | Example |
| First Character (Required) |
M | O | F |
1 |
This indicates the type of the element.
|
M18R1: This would mean a Multiple Choice Question. |
|---|---|---|---|---|
| Starting from Second Character (Required) |
[0-9]Digits only |
1+ | This indicates the key of the element. Both the type and the key can be found from the form builder itself. | M18R1: This would mean a Multiple Choice Question whose key is 18. |
| After the key digits (Optional) |
R |
1 | This indicates if we are going to choose a particular row of an element. This is applicable only for the following elements:
If this is absent for the elements above, then summation of all rows will be considered. |
M18R1: We are going to choose a row. |
| After row identifier (Optional) |
[0-9]Digits only |
1+ | The row of the element. It starts from position 0. | M18R1: We are considering the second row. |
#3.2: Expression Syntax:
We use the very popular JavaScript Expression Evaluator by Silent Matt. Quoting directly from his Github repository, the following rules apply for the expression syntax.
The parser accepts a pretty basic grammar. Operators have the normal precidence — f(x,y,z) (function calls), ^ (exponentiation), *, /, and % (multiplication, division, and remainder), and finally +, -, and || (addition, subtraction, and string concatenation) — and bind from left to right (yes, even exponentiation… it’s simpler that way).
There’s also a “,” (comma) operator that concatenates values into an array. It’s mostly useful for passing arguments to functions, since it doesn’t always behave like you would think with regards to multi-dimensional arrays. If the left value is an array, it pushes the right value onto the end of the array, otherwise, it creates a new array “[left, right]“. This makes it impossible to create an array with another array as it’s first element. Function operators
The parser has several built-in “functions” that are actually operators. The only difference from an outside point of view, is that they cannot be called with multiple arguments and they are evaluated by the simplify method if their arguments are constant.
Function Description sin(x) Sine of x (x is in radians) cos(x) Cosine of x (x is in radians) tan(x) Tangent of x (x is… well, you know) asin(x) Arc sine of x (in radians) acos(x) Arc cosine of x (in radians) atan(x) Arc tangent of x (in radians) sqrt(x) Square root of x. Result is NaN (Not a Number) if x is negative. log(x) Natural logarithm of x (not base-10). It’s log instead of ln because that’s what JavaScript calls it. abs(x) Absolute value (magnatude) of x ceil(x) Ceiling of x — the smallest integer that’s >= x. floor(x) Floor of x — the largest integer that’s <= x round(x) X, rounded to the nearest integer, using “gradeschool rounding”. exp(x) ex (exponential/antilogarithm function with base e) Pre-defined functions
Besides the “operator” functions, there are several pre-defined functions. You can provide your own, by binding variables to normal JavaScript functions. These are not evaluated by simplify.
Function Description random(n) Get a random number in the range [0, n). If n is zero, or not provided, it defaults to 1. fac(n) n! (factorial of n: “n * (n-1) * (n-2) * … * 2 * 1″) min(a,b,…) Get the smallest (“minimum”) number in the list max(a,b,…) Get the largest (“maximum”) number in the list pyt(a, b) Pythagorean function, i.e. the c in “c2 = a2 + b2“ pow(x, y) xy. This is exactly the same as “x^y”. It’s just provided since it’s in the Math object from JavaScript atan2(y, x) arc tangent of x/y. i.e. the angle between (0, 0) and (x, y) in radians.
#3.3: Examples:
A few examples of valid mathematical evaluators would be
(M1*(20+M6+M5))+(M2*(15+M8))+(M3*12)+(M4*(10+M9))+((M1*(20+M6+M5))+(M2*(15+M8))+(M3*12)+(M4*(10+M9)))*0.125 The one used in our Food Order Form.
(M1+M2)+(M8+M9)+(M10+M11)+(M6+M7*2)+(M3+M4R0*10+M4R1*5+M4R2*20+M5) The one used in our Service Cost Estimator.
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