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Pine Script Fundamentals

From Idea to Algorithm

You have a manual trading strategy for AUD/USD. Now, it's time to translate that logic into code. We'll use Pine Script, the programming language of the TradingView platform, to turn your rules into an automated system. This lets you backtest your ideas on historical data and execute trades without constant monitoring.

Every Pine Script file starts by declaring what it is: an indicator or a strategy. Since your goal is to backtest and potentially automate trades, we will focus on strategies.

  • Indicators (indicator()) draw lines, shapes, or text on your chart. Think of Moving Averages or the RSI. They provide visual information but cannot execute trades.
  • Strategies (strategy()) can do everything an indicator can, but they can also place, modify, and cancel simulated buy and sell orders. This is what enables backtesting.

Strategies are specific scripts, written in Pine Script language, which are able to send, modify, execute, and cancel buy or sell orders and simulate real trading right on your chart.

The fundamental structure of a strategy script is simple. It begins with a version declaration and the strategy() function call, which sets up the basic properties of your algorithm.

// © YourName
//@version=5
strategy("My AUD/USD Strategy", shorttitle="AUDUSD Strat", overlay=true)

// Strategy logic will go here

// Example: Enter a long position on the first bar
if bar_index == 0
    strategy.entry("My Long Entry", strategy.long)

In the example above, strategy() tells Pine Script to prepare for backtesting. The overlay=true argument makes the script draw its signals directly on the main price chart instead of in a separate pane below. The rest of your code will define the specific conditions for entering and exiting trades based on your 42% win rate strategy.

Handling Market Data

Pine Script is designed to work with time-series data. Every piece of market information, like the opening price, closing price, or an indicator's value, is not a single number but an array of numbers stretching back in time. This special data type is called a s.

Built-in variables like open, high, low, and close are all series. When your script runs on a chart, it executes once for every historical bar. The expression close gives you the closing price of the current bar the script is evaluating. To access previous values, you use the history-referencing operator []. For example, close[1] gives you the closing price of the previous bar, and close[10] gives you the price from 10 bars ago. This mechanism is the key to backtesting, as it allows your logic to analyze past price action.

While most data you'll work with is a series, the individual values within them have basic types like float (decimal numbers for price), int (whole numbers for counting bars), and bool (true/false values for conditions). Your trading logic will often generate a boolean series, like is_bullish_condition = close > open, which will be true for all bars that closed higher than they opened.

Setting Up for AUD/USD

Working with Forex pairs requires careful attention to price precision. For AUD/USD, a price might look like 0.6650. The smallest standard unit of movement is called a s. For most pairs, including AUD/USD, a pip is a change in the fourth decimal place (0.0001). When you set profit targets or stop losses, it's often more robust to define them in pips rather than absolute price offsets.

Calculating the pip value of a price movement is a simple subtraction and division.

Pips=∣Price2−Price1∣0.0001\text{Pips} = \frac{ | \text{Price}_2 - \text{Price}_1 | }{ 0.0001 }

To make your strategy flexible, you should define your key parameters, like the number of pips for a stop-loss, as input variables. This lets you change them from the script's settings menu without editing the code. It's essential for testing and optimizing your strategy's performance.

//@version=5
strategy("My AUD/USD Strategy", shorttitle="AUDUSD Strat", overlay=true)

// Define strategy parameters as inputs
inp_take_profit_pips = input.float(100, title="Take Profit in Pips")
inp_stop_loss_pips = input.float(50, title="Stop Loss in Pips")

// Convert pips to absolute price values
// syminfo.mintick gives the smallest possible price change (e.g., 0.00001 for a 5-decimal broker)
pip_value = 0.0001

take_profit_amount = inp_take_profit_pips * pip_value
stop_loss_amount = inp_stop_loss_pips * pip_value

// We will use these calculated amounts in our strategy.exit() function later

With this foundation, you can now begin scaffolding your specific trading rules. You have the script structure, a way to handle historical data, and a method for defining flexible, AUD/USD-specific parameters.