Cos¶

Overview¶

The Cos expression computes the cosine of a numeric value in radians. It is a unary mathematical expression that wraps the standard math.cos function and returns a double-precision floating-point result.

Syntax¶

COS(expr)

cos(col("column_name"))

Arguments¶

Argument	Type	Description
child	Expression	A numeric expression representing an angle in radians

Return Type¶

DoubleType - Returns a double-precision floating-point number representing the cosine value.

Supported Data Types¶

All numeric data types (IntegerType, LongType, FloatType, DoubleType, DecimalType)
Input values are implicitly converted to double before computation

Algorithm¶

Inherits from UnaryMathExpression which handles the core evaluation logic
Applies math.cos function to the child expression's evaluated result
Input value is treated as an angle measured in radians
Leverages Scala's standard math library for the actual cosine computation
Returns null if the input expression evaluates to null

Partitioning Behavior¶

This expression preserves partitioning:

Does not require data shuffling across partitions
Can be computed independently on each partition
Maintains existing data distribution patterns

Edge Cases¶

Null handling: Returns null if the input expression is null
Infinite values: COS(∞) returns NaN (Not a Number)
NaN input: COS(NaN) returns NaN
Very large values: May lose precision due to floating-point limitations
Range: Always returns values between -1.0 and 1.0 for finite inputs

Code Generation¶

This expression supports Tungsten code generation through its parent class UnaryMathExpression, which generates efficient Java code that directly calls Math.cos() method instead of using interpreted evaluation.

Examples¶

-- Basic usage
SELECT COS(0);
-- Result: 1.0

-- Using with PI
SELECT COS(3.14159265359);
-- Result: -1.0

-- Using with column data
SELECT angle_radians, COS(angle_radians) as cosine_value 
FROM measurements;

// DataFrame API usage
import org.apache.spark.sql.functions.cos

df.select(cos($"angle_column"))

// With column transformation
df.withColumn("cosine_result", cos($"radians_column"))