TradingView Indicator: Volume Momentum

study(title ="TheLark Volume Momentum",overlay=false)

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//          VOLUME MOMENTUM BY THELARK         //
//                 ~ 2-18-14 ~                 //
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//    https://www.tradingview.com/u/TheLark    //
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// For the momentum trader there are plenty of price momentum indicators,
// here's one that tracks the volume's momentum. Rising momentum in both price and volume
// is great for any momentum trader.
// Add this to your chart, play with the settings, and maybe you'll notice something new!
// Follow me on TradingView for more (and future) indicators/ ideas! ~ TheLark

//inputs
Length = input(14,minval=1)
atype = input(1,minval=1,maxval=3,title="1=sma, 2=ema, 3=wma")
mv = input(false, title="Multiply the volume?")
cc = input(false,title="Change color?")
//calc
avg = atype == 1 ? sma(volume,Length) : atype == 2 ? ema(volume,Length) : wma(volume,Length)
avgm = mv ? (avg - avg[Length]) * volume : (avg - avg[Length])
//plot
col = cc and avgm >= avgm[1] ? #0094FF : #FF006E
plot(avgm,style=histogram,linewidth=5,color=col)