Pine v5 script - why isn't this percentage conversion working?

Question

I have a TradingView Pine v5 strategy script that buys if the price closes a certain percentage below the set EMA level and sells if the price closes a certain percentage above the same EMA level.

Here's the working code for that:

// EMA Length
emaLength = input.int(title="EMA Length", defval=200, minval=0)

// EMA Price Percentages
emaPercBuy = input.float(title="Buy % Below EMA", defval=1.006, minval=0, step=0.001)      // 1.006 means 0.6%
emaPercSell = input.float(title="Sell % Above EMA", defval=1.006, minval=0, step=0.001)    // 1.006 means 0.6%

// EMA Line Function
emaLine = ta.ema(close, emaLength)

// EMA Plot line
plot(emaLine, color=close[1] > emaLine and close > emaLine ? colorGreen : colorRed, linewidth=2)

// Buy and Sell
longCond = close < emaLine/emaPercBuy
shortCond = close > emaLine*emaPercSell

defval=1.006 is 0.6% as a decimal and the line longCond = close < emaLine/emaPercBuy divides the EMA by that decimal number (aka "emaPercBuy") to reduce the EMA level by -0.6%. That all works fine, but it looks messy putting 1.006 and I want to be able to put 0.6 in the input.

That means making the code do a calculation so if I do 0.6 +100 /100 that converts it back to what the code needs to use 1.006

With that in mind I altered the code to allow normal looking percentages to be put in, but this doesn't work - it doesn't show any trades on the chart:

// EMA Length
emaLength = input.int(title="EMA Length", defval=200, minval=0)

// EMA Price Percentages
emaPercBuy = input.float(title="Buy % Below EMA", defval=0.6, minval=0, step=0.1)
emaPercSell = input.float(title="Sell % Above EMA", defval=0.6, minval=0, step=0.1)

// EMA Line Function
emaLine = ta.ema(close, emaLength)

// EMA Plot line
plot(emaLine, color=close[1] > emaLine and close > emaLine ? colorGreen : colorRed, linewidth=2)

// Buy and Sell
longCond = close < emaLine/emaPercBuy+100/100
shortCond = close > emaLine*emaPercSell+100/100

The line close < emaLine/emaPercBuy+100/100 should be the right calculation but it's not working - no trades appear on the chart unlike with the first block of code above that does work - but that looks messy with 1.006 to mean 0.6%.

I don't know why doing +100/100 hasn't fixed it and since that is the correct calculation, I don't know what else I could try. It seems even though the code compiles, there's something simple I have overlooked?

Thanks in advance to anyone Pine coders that can answer this.

score 1 · Accepted Answer · answered Dec 11 '22 at 17:02

With longCond = close < emaLine/emaPercBuy+100/100, you are simply adding 1 to the result of emaLine/emaPercBuy.

That expression will be evaluated as (emaLine/emaPercBuy) + (100/100).

I would do this in another way. I would get the percentage value in place like so:

emaPercBuy = input.float(title="Buy % Below EMA", defval=0.6, minval=0, step=0.001) * 0.01

Then calculate the value without modifying emaPercBuy later on like below:

longCond = (emaLine * (1 - emaPercBuy))

Otherwise, you need to convert emaPercBuy to percentage every time you use it.

Pine v5 script - why isn't this percentage conversion working?

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