examples: simple linear regression

examples/linear_regression/.gitignore

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+simple_linear_regression

examples/linear_regression/simple_linear_regression.v

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+import math
+
+struct LinearResult {
+	r2                         f64
+	intercept                  f64
+	slope                      f64
+	dependent_variable_means   f64
+	independent_variable_means f64
+}
+
+fn linearrelationship(independent_variable []int, dependent_variable []int) LinearResult {
+	// Objective :
+	// Find what is the linear relationship between two dataset X and Y?
+	// x := independent variable
+	// y := dependent variable
+	mut sum_r2_x := 0
+	mut sum_r2_y := 0
+	mut sum_xy := 0
+	mut sum_x := 0
+	mut sum_y := 0
+	for i in independent_variable {
+		sum_x += i
+		sum_r2_x += i * i
+	}
+	for yi in dependent_variable {
+		sum_y += yi
+		sum_r2_y += yi * yi
+	}
+	x_means := sum_x / independent_variable.len
+	y_means := sum_y / dependent_variable.len
+	for index, x_value in independent_variable {
+		sum_xy += x_value * dependent_variable[index]
+	}
+	// /Slope = (∑y)(∑x²) - (∑x)(∑xy) / n(∑x²) - (∑x)²
+	slope_value := f64((sum_y * sum_r2_x) - (sum_x * sum_xy)) / f64((sum_r2_x * independent_variable.len) - (sum_x * sum_x))
+	// /Intercept = n(∑xy) - (∑x)(∑y) / n(∑x²) - (∑x)²
+	intercept_value := f64((independent_variable.len * sum_xy) - (sum_x * sum_y)) / f64((independent_variable.len * sum_r2_x) - (sum_x * sum_x))
+	// Regression equation = Intercept + Slope x
+	// R2 = n(∑xy) - (∑x)(∑y) / sqrt([n(∑x²)-(∑x)²][n(∑y²)-(∑y)²]
+	r2_value := f64((independent_variable.len * sum_xy) - (sum_x * sum_y)) / math.sqrt(f64((sum_r2_x * independent_variable.len) - (sum_x * sum_x)) * f64((sum_r2_y * dependent_variable.len) - (sum_y * sum_y)))
+	return LinearResult{
+		r2: r2_value
+		intercept: intercept_value
+		slope: slope_value
+		independent_variable_means: x_means
+		dependent_variable_means: y_means
+	}
+}
+
+fn main() {
+	independent_variable := [4, 5, 6, 7, 10]
+	dependent_variable := [3, 8, 20, 30, 12]
+	result := linearrelationship(independent_variable, dependent_variable)
+	println(result)
+}