MA Alert

//@version=2
//

study("MA Alert",overlay=true)

//
// Description: Create alert when MA changes direction

//
// - INPUTS

// Medium Fast MA - type, source, length
ma_type   = input(defval="HullMA", title="MA Type: SMA, EMA, WMA, VWMA, SMMA, DEMA, TEMA, HullMA, ZEMA, TMA, SSMA ( case sensitive )", type=string)
ma_len    = input(defval=21, title="MA - Length", minval=1)
ma_src    = input(close, title="MA - Source")
// - /INPUTS

// - FUNCTIONS

// Returns MA input selection variant, default to SMA if blank or typo.
variant(type, src, len) =>
    v1 = sma(src, len)                                                  // Simple
    v2 = ema(src, len)                                                  // Exponential
    v3 = wma(src, len)                                                  // Weighted
    v4 = vwma(src, len)                                                 // Volume Weighted
    v5 = na(v5[1]) ? sma(src, len) : (v5[1] * (len - 1) + src) / len    // Smoothed
    v6 = 2 * v2 - ema(v2, len)                                          // Double Exponential
    v7 = 3 * (v2 - ema(v2, len)) + ema(ema(v2, len), len)               // Triple Exponential
    v8 = wma(2 * wma(src, len / 2) - wma(src, len), round(sqrt(len)))   // Hull
    v11 = sma(sma(src,len),len)                                         // Triangular
    // SuperSmoother filter
    // © 2013  John F. Ehlers
    a1 = exp(-1.414*3.14159 / len)
    b1 = 2*a1*cos(1.414*3.14159 / len)
    c2 = b1
    c3 = (-a1)*a1
    c1 = 1 - c2 - c3
    v9 = c1*(src + nz(src[1])) / 2 + c2*nz(v9[1]) + c3*nz(v9[2])
    // Zero Lag Exponential
    ema1 = ema(src, len)
    ema2 = ema(ema1, len)
    v10 = ema1+(ema1-ema2)
    // return variant, defaults to SMA if input invalid.
    type=="EMA"?v2 : type=="WMA"?v3 : type=="VWMA"?v4 : type=="SMMA"?v5 : type=="DEMA"?v6 : type=="TEMA"?v7 : type=="HullMA"?v8 : type=="SSMA"?v9 : type=="ZEMA"?v10 : type=="TMA"? v11: v1

// - /FUNCTIONS

// - SERIES VARIABLES
// MA's
ma_series  = variant(ma_type, ma_src, ma_len)
// - /SERIES VARIABLES

// Get Direction From Moving Average
direction = rising(ma_series,3) ? 1 : falling(ma_series,3) ? -1 : 0
// Count Bars going up or going down
up = direction>0? na(up[1])? 1 : up[1]+1 : 0
down = direction<0? na(down[1])? 1 : down[1]+1 : 0

// - /SERIES VARIABLES

// - PLOTTING
// Plot MA series and color it according too direction
plot(ma_series, title="MA Plot", color=direction<0?red:direction>0?green:aqua, linewidth=3, transp=0)

// - /PLOTTING

// - ALERTING
c_alert = up==1 or down==1
alertcondition(c_alert, title="MA Alert", message="MA Alert")
alertcondition(up==1, title="MA Buy Alert", message="MA Buy Alert")
alertcondition(down==1, title="MA Sell Alert", message="MA Sell Alert")

//
// show an Arrow only when alert condition is met and the bar closed.
plotshape(down[1]==1,title= "MA Sell Alert Completed", location=location.abovebar, color=red, transp=0, style=shape.arrowdown, text="SELL",size=size.auto,offset=-1)
plotshape(up[1]==1,title= "MA Buy Alert Completed", location=location.belowbar, color=green, transp=0, style=shape.arrowup, text="BUY",size=size.auto,offset=-1)

// - /ALERTING

// /eof