Hello Nicholas,
When I am using style(line,5) in your below written code it is providing error. Appreciate if you please tell me how to incorporate style(line,5) in the following code:

//PRC_Std and Ste LinRegChannel | indicator
//Standard Deviation and Standard Error
//Linear Regression Channel
//12.03.2019
//Nicolas @ www.prorealcode.com
//Sharing ProRealTime knowledge

defparam drawonlastbaronly=true
defparam calculateonlastbars=1000
// --- settings
// chnlper = 200, sdsr = 1, devmul = 1.62, c1 = 153, c2 = 51, c3 =0
lookback= chnlper //channel period
ChannelType = sdsr //1= Standard Deviation ; 2= Standard Erro
NbDeviation = devmul //Deviation multiplier
colorRed = C1
colorGreen = C2
colorBlue = C3
// --- end of settings

sumx = 0
sumy = 0
sumxy = 0
sumx2 = 0

for cmpt = lookback downto 0 do
tmpx = cmpt
tmpy = close[cmpt]
sumy = sumy+tmpy
sumx = sumx+tmpx
sumx2 = sumx2 + (tmpx*tmpx)
sumxy = sumxy + (tmpy*tmpx)
next

n = lookback+1

if (sumx2 = sumx * sumx) then // protection to avoid infinite values
b = sumxy - sumx * sumy
else
b = (n * sumxy - sumx * sumy) / (n * sumx2 - sumx * sumx)
endif
a = (sumy - b * sumx) / n

//drawsegment(barindex[lookback],a+b*lookback,barindex,a+b*0) coloured(colorRed,colorGreen,colorBlue)

//channel
if ChannelType = 1 then //Standard Deviation
dat = std[lookback]*NbDeviation
elsif ChannelType = 2 then
dat = ste[lookback]*NbDeviation
endif
drawsegment(barindex[lookback],(a+b*lookback)+dat,barindex,a+b*0+dat) coloured(colorRed,colorGreen,colorBlue)
drawsegment(barindex[lookback],(a+b*lookback)-dat,barindex,a+b*0-dat) coloured(colorRed,colorGreen,colorBlue)

return

Style.jpg