Change RSI Plot Range - Possible or not? - range

Question

We know that RSI plotting range is between 0 to 100.
Is it possible to change a plotted indicator line so that it will fluctuate in an extended range, say -50 to 100 ?
In simple way I want it to be (stretched) so I can easily draw trend line on the RSI line.
Attached photo is sample of what I mean on is perfect , one that I have is not like it.
I want the the RSI to cross the green and red area without affecting the movement of the indicator. I just want it to be stretching.
enter image description here
enter image description here
//#version=5
indicator(title="Relative Strength Index", shorttitle="RSI", format=format.price, precision=2, timeframe="", timeframe_gaps=true)
ma(source, length, type) =>
switch type
"SMA" => ta.sma(source, length)
"Bollinger Bands" => ta.sma(source, length)
"EMA" => ta.ema(source, length)
"SMMA (RMA)" => ta.rma(source, length)
"WMA" => ta.wma(source, length)
"VWMA" => ta.vwma(source, length)
rsiLengthInput = input.int(14, minval=1, title="RSI Length", group="RSI Settings")
rsiSourceInput = input.source(close, "Source", group="RSI Settings")
maTypeInput = input.string("SMA", title="MA Type", options=["SMA", "Bollinger Bands", "EMA", "SMMA (RMA)", "WMA", "VWMA"], group="MA Settings")
maLengthInput = input.int(50, title="MA Length", group="MA Settings")
up = ta.rma(math.max(ta.change(rsiSourceInput), 0), rsiLengthInput)
down = ta.rma(-math.min(ta.change(rsiSourceInput), 0), rsiLengthInput)
rsi = down == 0 ? 100 : up == 0 ? 0 : 100 - (100 / (1 + up / down))
rsiMA = ma(rsi, maLengthInput, maTypeInput)
rsicolor = rsi > 70 ? color.new(#ff0057, 0) : rsi < 30 ? color.new(#ff0057, 0) : #1056ee
plot(rsi, "RSI", color=rsicolor, linewidth=2, style=plot.style_stepline)
plot(rsiMA, "RSI-based MA", color=color.rgb(120, 206, 255))
OverBought1 = input.int(80, minval=1)
OverBought2 = input.int(90, minval=1)
OverSold1 = input.int(20, minval=1)
OverSold2 = input.int(10, minval=1)
OB1 = hline(OverBought1 , color=color.red, linestyle=hline.style_dashed)
OB2 = hline(OverBought2 , color=color.red, linestyle=hline.style_dashed)
OS1 = hline(OverSold1 , color=color.green, linestyle=hline.style_dashed)
OS2 = hline(OverSold2 , color=color.green, linestyle=hline.style_dashed)
fill(OB1 , OB2, color=color.rgb(255, 82, 82, 80), title="Red Zoon Fill")
fill(OS1 , OS2 , color=color.rgb(76, 175, 79, 80), title="Green Zoon Fill")
Any ideas, please?
Thank you!
Colin
Is it possible to change a plotted indicator line so that it will fluctuate in an extended range, say -50 to 100 ?
In simple way I want it to be (stretched) so I can easily draw trend line on the RSI line.
Attached photo is sample of what I mean on is perfect , one that I have is not like it.
I want the the RSI to cross the green and red area without affecting the movement of the indicator. I just want it to be stretching.

Answer 1

You can use normalize() function:
//#version=5
indicator("My script")
normalize(_src, _min, _max) =>
// Normalizes series with unknown min/max using historical min/max.
// _src : series to rescale.
// _min, _min: min/max values of rescaled series.
var _historicMin = 10e10
var _historicMax = -10e10
_historicMin := math.min(nz(_src, _historicMin), _historicMin)
_historicMax := math.max(nz(_src, _historicMax), _historicMax)
_min + (_max - _min) * (_src - _historicMin) / math.max(_historicMax - _historicMin, 10e-10)
rsi = ta.rsi(close, 20)
rsiNormalized = normalize(rsi, -50, 100)
plot(rsiNormalized)
hline(-50)
hline(100)
EDIT
In your case, since we know the scale will always be between 0 to 100, we can use math to solve the issue much more accurately:
//#version=5
indicator("My script")
rsi = ta.rsi(close, 20) // this will give a value between 0 to 100
// find the value compared to a scale of 100
rsiPerc = rsi / 100
// multiply by the new range to get the position of rsi on the new range
rsiOnNewScale = rsiPerc * 150
// place the newRsi on a scale of -50 to 100
newRsi = rsiOnNewScale - 50
plot(newRsi)
hline(-50)
hline(100)
Or in short:
//#version=5
indicator("My script")
rsi = ta.rsi(close, 20) // this will give a value between 0 to 100
newRsi = (rsi / 100 * 150) - 50
plot(newRsi)
hline(-50)
hline(100)