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Variables and Data Types 📊

Basic Data Types​

Pine Script has several fundamental data types:

// Numbers
float myPrice = 100.50
int myQuantity = 100

// Strings
string myText = "Hello"

// Booleans
bool isBullish = true

// Colors
color lineColor = color.blue

// Arrays
float[] prices = array.new_float(0)

Variable Declaration​

Using 'var' Keyword​

The var keyword creates variables that persist across bars:

//@version=5
indicator("Variable Example")

// Regular variable - recalculated every bar
myVar = close

// Persistent variable - only initialized once
var myPersistent = close

Series vs. Simple Variables​

// Simple (single value)
simpleValue = 100

// Series (value for each bar)
seriesValue = close

// Accessing historical values
previousClose = close[1]  // Previous bar's close
twoBarBack = close[2]    // Two bars back

Type Conversion​

// String to float
stringPrice = "100.5"
floatPrice = str.tostring(stringPrice)

// Float to integer
floatNum = 100.5
intNum = int(floatNum)

// Number to string
price = 100.5
priceString = str.tostring(price)

Arrays​

Creating Arrays​

// Create new arrays
var float[] prices = array.new_float(0)
var string[] labels = array.new_string(0)

// Initialize with values
var int[] numbers = array.from(1, 2, 3, 4, 5)

Array Operations​

//@version=5
indicator("Array Operations")

var float[] prices = array.new_float(0)

// Add value
array.push(prices, close)

// Get value
firstPrice = array.get(prices, 0)

// Set value
array.set(prices, 0, high)

// Get size
size = array.size(prices)

// Remove value
array.pop(prices)

Matrices​

//@version=5
indicator("Matrix Example")

// Create a 2x2 matrix
var matrix<float> m = matrix.new<float>(2, 2, 0.0)

// Set values
matrix.set(m, 0, 0, 1.0)
matrix.set(m, 0, 1, 2.0)
matrix.set(m, 1, 0, 3.0)
matrix.set(m, 1, 1, 4.0)

// Get value
value = matrix.get(m, 0, 0)

Scope​

Global Scope​

//@version=5
indicator("Scope Example")

// Global variable
globalVar = 100

// Function using global variable
myFunction() =>
    globalVar + 50

Local Scope​

myFunction() =>
    // Local variable
    localVar = 100
    localVar + 50

// localVar is not accessible here

Practice Exercises​

1. Price History Array​

//@version=5
indicator("Price History")

// Store last 5 closing prices
var float[] closePrices = array.new_float(5, close)

// Update array
array.unshift(closePrices, close)
array.pop(closePrices)

// Calculate average
sum = array.sum(closePrices)
avg = sum / array.size(closePrices)

plot(avg, "5-bar Average")

2. Dynamic Labels​

//@version=5
indicator("Dynamic Labels")

var string[] labels = array.new_string(0)

if (close > high[1])
    array.push(labels, "New High")
if (close < low[1])
    array.push(labels, "New Low")

if (array.size(labels) > 10)
    array.shift(labels)

label.new(bar_index, high, array.get(labels, array.size(labels)-1))
Pro Tips
  • Use var for variables that should persist
  • Be mindful of type conversion
  • Arrays are great for historical data
  • Keep track of array sizes

Common Pitfalls​

Watch Out For

❌ Forgetting to initialize arrays ❌ Mixing types without conversion ❌ Not handling empty arrays ❌ Ignoring scope rules

Next Steps​

Ready to learn about operators and control flow? Move on to the next chapter! 🚀