-- Id: 1379
-- More information about this indicator can be found at:
-- http://fxcodebase.com/code/viewtopic.php?f=17&t=1966

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function Init()
    indicator:name("Force Index");
    indicator:description("Dr. Alexander Elder's Force Index. The indicator combines price movements and volume to measure the strength of bulls and bears in the market.");
    indicator:requiredSource(core.Bar);
    indicator:type(core.Oscillator);
    indicator:setTag("group", "Volume Indicators");

    indicator.parameters:addGroup("Calculation");
    indicator.parameters:addBoolean("SM", "Smooth", "Choose false to see the RAW Force Index value", true);
    indicator.parameters:addInteger("N", "Smoothing Periods", "", 13, 1, 1000);

    indicator.parameters:addGroup("Style");
    indicator.parameters:addColor("Up", "Up Color", "", core.rgb(0, 255, 0));
	indicator.parameters:addColor("Down", "Down Color", "", core.rgb(255,0, 0));
    indicator.parameters:addInteger("widthFI", "Indicator Line Width", "", 1, 1, 5);
    indicator.parameters:addInteger("styleFI", "Indicator Line Style", "", core.LINE_SOLID);
    indicator.parameters:setFlag("styleFI", core.FLAG_LINE_STYLE);
	
	indicator.parameters:addString("Method", "Presentation Method", "Method" , "Line");
    indicator.parameters:addStringAlternative("Method", "Line", "Line" , "Line");
    indicator.parameters:addStringAlternative("Method", "Channel", "Channel" , "Channel");
	indicator.parameters:addStringAlternative("Method", "Bar", "Bar" , "Bar");
	indicator.parameters:addInteger("transparency", "Channel transparency (%)", "", 70, 0, 100);
 
end

local source;
local first;
local first1;
local RawFI;
local FI;
local EMA;
local SM;
local Method;
local Zero;
function Prepare(nameOnly)
    source = instance.source;
    first1 = source:first() + 1;
    SM = instance.parameters.SM;
	Method= instance.parameters.Method;

    assert(source:supportsVolume(), "The source must have volume");

    local name;
    name = profile:id() .. "(" .. source:name() .. "," ;
    if SM then
        name = name .. "EMA(" .. instance.parameters.N .. "))";
    else
        name = name .. "RAW)";
    end
    instance:name(name);
    if nameOnly then
        return;
    end

    RawFI = instance:addInternalStream(first1, 0);
    if SM then
        EMA = core.indicators:create("EMA", RawFI, instance.parameters.N);
        first = EMA.DATA:first();
    else
        first = first1;
    end

	if Method=="Line" then 
    FI = instance:addStream("FI", core.Line, name, "FI", instance.parameters.Up, first);
	FI:setWidth(instance.parameters.widthFI);
    FI:setStyle(instance.parameters.styleFI);
	elseif Method=="Bar" then 
	FI = instance:addStream("FI", core.Bar, name, "FI", instance.parameters.Up, first);
	else
	FI = instance:addStream("FI", core.Line, name, "FI", instance.parameters.Up, first);
	Zero=  instance:addInternalStream(first, 0)
	instance:createChannelGroup("Channel", "Channel", FI, Zero, instance.parameters.Up, 100 - instance.parameters.transparency);

	end
	
    FI:setPrecision(5);

    FI:addLevel(0);
end

function Update(period, mode)
    if period >= first1 then
        RawFI[period] = (source.close[period] - source.close[period - 1]) * source.volume[period];
    end
	
	if Method=="Channel" then 
	Zero[period]=0;
	end

    if period < first then
	return;
	end
	
	
        if SM then
            EMA:update(mode);
            FI[period] = EMA.DATA[period];
        else
            FI[period] = RawFI[period];
        end
	if Method~="Line" then 
		if 	FI[period]>0 then
		FI:setColor(period, instance.parameters.Up);
		else
		FI:setColor(period, instance.parameters.Down);
		end
	end
     
end