Linear Regression Channel

// This source code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// © LonesomeTheBlue

//@version=4
study("Linear Regression Channel", overlay = true, max_bars_back = 1000, max_lines_count = 300)
src = input(defval = close, title = "Source")
len = input(defval = 100, title = "Length", minval = 10)
devlen = input(defval = 2., title = "Deviation", minval = 0.1, step = 0.1)
extendit = input(defval = true, title = "Extend Lines")
showfibo = input(defval = false, title = "Show Fibonacci Levels")
showbroken = input(defval = true, title = "Show Broken Channel")
upcol = input(defval = color.lime, title = "Up Color")
dncol = input(defval = color.red, title = "Down Color")
widt = input(defval = 2, title = "Line Width")

var fibo_ratios = array.new_float(0)
var colors = array.new_color(2)
if barstate.isfirst
    array.unshift(colors, upcol)
    array.unshift(colors, dncol)
    array.push(fibo_ratios, 0.236)
    array.push(fibo_ratios, 0.382)
    array.push(fibo_ratios, 0.618)
    array.push(fibo_ratios, 0.786)



get_channel(src, len)=>
    mid = sum(src, len) / len
    slope = linreg(src, len, 0) - linreg(src, len, 1)
    intercept  = mid - slope * floor(len / 2) + ((1 - (len % 2)) / 2) * slope
    endy = intercept  + slope * (len - 1) 
    dev = 0.0
    for x = 0 to len - 1
        dev := dev + pow(src[x] - (slope * (len - x) + intercept), 2)
    dev := sqrt(dev/len)
    [intercept, endy, dev, slope]

[y1_, y2_, dev, slope] = get_channel(src, len)

outofchannel = (slope > 0 and close < y2_ - dev * devlen) ? 0 : (slope < 0 and close > y2_ + dev * devlen) ? 2 : -1

var reglines = array.new_line(3)
var fibolines = array.new_line(4)
for x = 0 to 2
    if not showbroken or outofchannel != x or nz(outofchannel[1], -1) != -1
        line.delete(array.get(reglines, x))
    else
        line.set_color(array.get(reglines, x), color = color.blue)
        line.set_width(array.get(reglines, x), width = 2)
        line.set_style(array.get(reglines, x), style = line.style_dotted)
        line.set_extend(array.get(reglines, x), extend = extend.none)
    
    array.set(reglines, x, 
              line.new(x1 = bar_index - (len - 1), 
                       y1 = y1_ + dev * devlen * (x - 1), 
                       x2 = bar_index, 
                       y2 = y2_ + dev * devlen * (x - 1),
                       color = array.get(colors, round(max(sign(slope), 0))),
                       style =  x % 2 == 1 ? line.style_solid : line.style_dashed,
                       width = widt,
                       extend = extendit ? extend.right : extend.none))
if showfibo
    for x = 0 to 3
        line.delete(array.get(fibolines, x))
        array.set(fibolines, x, 
                  line.new(x1 = bar_index - (len - 1), 
                           y1 = y1_ - dev * devlen + dev * devlen * 2 * array.get(fibo_ratios, x), 
                           x2 = bar_index, 
                           y2 = y2_ - dev * devlen + dev * devlen * 2 * array.get(fibo_ratios, x),
                           color = array.get(colors, round(max(sign(slope), 0))),
                           style =  line.style_dotted,
                           width = widt,
                           extend = extendit ? extend.right : extend.none))
    
var label sidelab = label.new(x = bar_index - (len - 1), y = y1_, text = "S",  size = size.large)
txt = slope > 0 ? slope > slope[1] ? "⇑" : "⇗" : slope < 0 ? slope < slope[1] ? "⇓" : "⇘" : "⇒"
stl = slope > 0 ? slope > slope[1] ? label.style_label_up : label.style_label_upper_right : slope < 0 ? slope < slope[1] ? label.style_label_down :  label.style_label_lower_right : label.style_label_right
label.set_style(sidelab, stl)
label.set_text(sidelab, txt)
label.set_x(sidelab, bar_index - (len - 1))
label.set_y(sidelab, slope > 0 ? y1_ - dev * devlen : slope < 0 ? y1_ + dev * devlen : y1_)
label.set_color(sidelab, slope > 0 ? upcol : slope < 0 ? dncol : color.blue)

alertcondition(outofchannel, title='Channel Broken', message='Channel Broken')