Using math formulas for generating data
php-RGraph provides two php functions in addition to the rgraph_chart and
rgraph_options classes. These two functions are used to generate
data for line or scatter charts.
- getDataviaFormula
- calculate_Regression
calculate_Regression
- Description
- function does a basic regression analysis.
It provides three builtin calculations (all based on the linear regression model)
which are described by following functions:
- f(x) = ax + b (linear regression)
- f(x) = abx (exponential regression)
- f(x) = axb (exponential regression)
- Function Call
- calculate_Regression($x_values, $y_values, $user_formula=null, $number_format="en", $precision=2)
- Parameter
-
$x_values and $y_values are arrays of numerical values
$user_formula - you may provide own regression formula which then will be used
$number_format - defines the number format of calculated output formula
$precision - defines the decimal scale of calculated output formula
- Return Value
- an array containing arrays of x/y pairs and a calculated regression formula
- Example
-
$result = calculate_Regression($x_values, $y_values);
$data = $result['values'];
$formula = $result['formula'];
getDataviaFormula
- Description
- function generates data based on a provided math formula
- Function Call
- getDataviaFormula($formula, $x_interval=1, $x_min=0, $x_max=5, $max_iterations = 500)
- Parameter
- $formula - Notation of your formula is derived by script-language "PHP". Pls. read following related information:
- You may specify formula with or without equal sign e. g. formula="y = x * e^x" or formula="x * e^x"
- Independent variable must be set to "x"
- Creation of data is controlled by four parameters:
- "$x_min" - x-value for start of calculation
- "$x_max" - x-value for end of calculation
- "$x_interval" - x-increment for calculation
- "$max_iterations" maximum of calculation steps
Calculation stops if either x_max or $max_iterations are reached.
- Constants:
- Pi (π): "pi"
- Euler's number (e): "e"
- Operators:
- Add: "+"
- Subtract: "-"
- Multiply: "*"
- Divide: "/"
- Power: "^"
- Functions
- sin
- sinh
- arcsin
- asin
- arcsinh
- asinh
- cos
- cosh
- arccos
- acos
- arccosh
- acosh
- tan
- tanh
- arctan
- atan
- arctanh
- atanh
- sqrt
- abs
- ln
- log10
- log
- Return Value
- an associative array with keys
"x_values", "y_values" or
in case of an error "error" has error infos stored
and x_values and y_values are empty (not set).
- Example
- $data = getDataviaFormula("y=2*e^-(0.2 * x)*sin(x * 2*pi)", 0.1, 0, 20);
$x_values = $data['x_values'];
$y_values = $data['y_values'];