moving average spread Leaf_West Style

//
// by Jayy
//  Moving average spread indicator also known also known as percentage Price Oscillator
// Leaf West uses 20 for the short EMA, 50 for the long EMA and 10 SMA for the signal line.
// http://tradingwithleafwest.net/
study(title = "moving average spread", shorttitle="Moving Average Spread Leaf_West style", overlay=false)

source=close

// Slow line difference between ema 20 and ema 50 expressed as a percent
lengtha=input(20)
emaa=ema(source, lengtha)

length1=input(50)
ema1=ema(source, length1)

d1=emaa-ema1
PPOfraction= d1/ema1
PPOpercent= 100 *PPOfraction
length2=input(10)
sma3=sma(PPOpercent, length2)

pa=plot(PPOpercent, color=black, linewidth=1)
pb=plot(sma3, color= red, linewidth=1)

hline(0)