Rory Claasen

Linq Median

• 1 min read
#Code Snippet

Extension methods for calculating the median a sequence of numbers. Similar to Linq Product, this is using the INumber interface from Generic Math.

MedianExtensions.cs
public static TNumber Median<TNumber>(this IEnumerable<TNumber> source) where TNumber : struct, INumber<TNumber>
    => Median(new ReadOnlySpan<TNumber>(source.ToArray()));


public static TNumber Median<TNumber>(this TNumber[] source) where TNumber : struct, INumber<TNumber>
    => Median(new ReadOnlySpan<TNumber>(source));


public static TNumber Median<TNumber>(this ReadOnlySpan<TNumber> source) where TNumber : struct, INumber<TNumber>
{
    if (source.IsEmpty)
    {
        return TNumber.Zero;
    }


    if (source.Length == 1)
    {
        return source[0];
    }


    if (source.Length == 2)
    {
        checked
        {
            return (source[0] + source[1]) / TNumber.CreateChecked(2);
        }
    }


    var sourceCopy = new Span<TNumber>(source.ToArray());
    MemoryExtensions.Sort(sourceCopy);


    checked
    {
        if (sourceCopy.Length % 2 == 0)
        {
            return (sourceCopy[sourceCopy.Length / 2] + sourceCopy[(sourceCopy.Length / 2) - 1]) / TNumber.CreateChecked(2);
        }


        return sourceCopy[sourceCopy.Length / 2];
    }
}
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