Heikin-Ashi Simple Strategy

strategy("Heikin-Ashi Color change Strategy ",shorttitle="HAS color change ",overlay=true)
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res = input(title="Resolution", type=resolution, defval="60")
//Heikin ashi taken from trading view's funciton and resolusion added 
ha_t = heikinashi(tickerid)
ha_open = security(ha_t, res, open)
ha_close = security(ha_t, res, close)


golong = ha_close > ha_open 
goshort = ha_close < ha_open 

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strategy.entry("Buy",strategy.long,when = golong and year > 2015)
strategy.entry("Sell",strategy.short,when = goshort and year > 2015)