Automatic Trendlines – pinescript codes for Trading View platform

//@version=2
study("Trend Line", overlay=true)

//I like tips :D

//look back distance
shortl = input(20)
longl = input(100)

//establish timeline in bars

timeline = nz(timeline[1]) + 1

//find bottoms
 
middle = round(1) //half way through shortl  round(shortl/2)
//a = valuewhen(low[middle]==lowest(low, shortl), low[middle], 0) //what is lowest point in the short range
//whena = valuewhen(low[middle]==lowest(low, shortl), fixnan(timeline[middle]), 0) //when is lowest point in the range
a = valuewhen(low[middle]==lowest(low, shortl), low[middle], 0)
whena = valuewhen(low[middle]==lowest(low, shortl), fixnan(timeline[middle]), 0)

middlelong = round(longl/2)
//b= valuewhen(fixnan(low[middle])==lowest(low, shortl) , fixnan(low[middle]), 1) //
//whenb = valuewhen(fixnan(low[middle])==lowest(low, shortl) , timeline[middle], 1) //
b= valuewhen(fixnan(low[middlelong])==lowest(low, longl) , fixnan(low[middlelong]), 0) //
whenb = valuewhen(fixnan(low[middlelong])==lowest(low, longl) , fixnan(timeline[middlelong]), 0) //

b := b==a? valuewhen(fixnan(low[middlelong])==lowest(low, longl) , fixnan(low[middlelong]), 1) : b
whenb := b==a? valuewhen(fixnan(low[middlelong])==lowest(low, longl) , fixnan(timeline[middlelong]), 1) : whenb

//m = ((b-a)/(whenb-whena))
//trendprice = m*(timeline-whena-0) + a
//backtrendprice = m*(timeline-whena-middle) + a

m = (((b)-(a))/(whenb-whena))

trendprice = (m*(timeline-whena-0)) + a
backtrendprice = (m*(timeline-whena-middle)) + a


sametrend = a==fixnan(a[1]) and b==fixnan(b[1]) and a!=0 and b!=0 and whena!=whenb

//plot
plot(sametrend? trendprice: na, style=linebr, color=green, linewidth=2, offset=0, transp=50)
plot(sametrend? backtrendprice: na, style=linebr, color=green, linewidth=1, offset=-middle, transp=50)
forwardtrendprice = (m*(timeline-whena+middle)) + a
plot(sametrend? forwardtrendprice: na, style=linebr, color=green, linewidth=1, offset=middle, transp=70)

//find tops


a2 = valuewhen(high[middle]==highest(high, shortl), high[middle], 0) //
whena2 = valuewhen(high[middle]==highest(high, shortl), timeline[middle], 0) //

b2= valuewhen(fixnan(high[middlelong])==highest(high, longl) , fixnan(high[middlelong]), 0) //
whenb2 = valuewhen(fixnan(high[middlelong])==highest(high, longl) , fixnan(timeline[middlelong]), 0) //
b2 := b2==a2? valuewhen(fixnan(high[middlelong])==highest(high, longl) , fixnan(high[middlelong]), 1) : b2
whenb2 := b2==a2? valuewhen(fixnan(high[middlelong])==highest(high, longl) , fixnan(timeline[middlelong]), 1) : whenb2

m2 = ((b2-a2)/(whenb2-whena2))
trendprice2 = m2*(timeline-whena2-0) + a2
backtrendprice2 = m2*(timeline-whena2-shortl) + a2

sametrend2 = a2==fixnan(a2[1]) and b2==fixnan(b2[1]) and a2!=0 and b2!=0 and whena2!=whenb2


//plot
plot(sametrend2? trendprice2:na, style=linebr, color=red, linewidth=2, offset=-0, transp=50)
plot(sametrend2? backtrendprice2:na, style=linebr, color=red, linewidth=1, offset=-shortl, transp=50)
forwardtrendprice2 = (m2*(timeline-whena2+middle)) + a2
plot(sametrend2? forwardtrendprice2: na, style=linebr, color=red, linewidth=1, offset=middle, transp=70)