Linear Regression without using R - php

Question

I have a task which requires to generate the slope and interception of two sets of data by linear regression. According to the following link, it can be easily accomplished by R:
https://www.datacamp.com/community/tutorials/linear-regression-R
The codes are simply like
model <- lm(sales ~ youtube, data = marketing)
However, I will need to implement it in PHP. Is it possible ?

Answer 1

Normally you can do such operation easily in R.
But since you said you have to do it this time in PHP. You may use the following function:
<?php
function linear_regression($x, $y) {
// calculate number points
$n = count($x);
// ensure both arrays of points are the same size
if ($n != count($y)) {
trigger_error("linear_regression(): Number of elements in coordinate arrays do not match.", E_USER_ERROR);
}
// calculate sums
$x_sum = array_sum($x);
$y_sum = array_sum($y);
$xx_sum = 0;
$xy_sum = 0;
for($i = 0; $i < $n; $i++) {
$xy_sum+=($x[$i]*$y[$i]);
$xx_sum+=($x[$i]*$x[$i]);
}
// calculate slope
$m = (($n * $xy_sum) - ($x_sum * $y_sum)) / (($n * $xx_sum) - ($x_sum * $x_sum));
// calculate intercept
$b = ($y_sum - ($m * $x_sum)) / $n;
// return result
return array("m"=>$m, "b"=>$b);
}
?>
As an example, you may use the following codes to get the slope and intercept of the two sets of data:
$a=array();
$b=array();
array_push($a,$adata1);
array_push($a,$adata2);
array_push($a,$adata3);
array_push($a,$adata4);
array_push($b,$bdata1);
array_push($b,$bdata2);
array_push($b,$bdata3);
array_push($b,$bdata4);
$aa= linear_regression($a, $b);
$slope1= $aa["m"];
$intercept1= $aa["b"];