# DenseVector_Double A structure that contains a dense vector of double-precision, floating-point values. ``` struct DenseVector_Double ``` ## Overview You typically use dense vectors to represent the unknowns vector, *x*, and the right-hand-side vector, *b*, in the matrix equation *Ax = b.* A [`DenseVector_Double`](/documentation/Accelerate/DenseVector_Double) structure provides a pointer to its underlying data and a count of its number of elements. The following code shows an example of how to create a dense vector structure from an array of double-precision values. In this case, use [`withUnsafeMutableBufferPointer(_:)`](/documentation/Accelerate/AccelerateMutableBuffer/withUnsafeMutableBufferPointer(_:)) to pass a pointer to your collection. The [`DenseVector_Double`](/documentation/Accelerate/DenseVector_Double) structure is valid only during the execution of the closure. Don’t store or return the structure for later use. ```swift var vectorValues: [Double] = [10, 20, 30, 40] let vectorValuesCount = Int32(vectorValues.count) vectorValues.withUnsafeMutableBufferPointer { vectorValuesPtr in let vector = DenseVector_Double(count: vectorValuesCount, data: vectorValuesPtr.baseAddress!) // Perform operations using `vector`. } ``` ## Topics ### Initializers [`init(count:data:)`](/documentation/Accelerate/DenseVector_Double/init(count:data:)) Creates a new vector of double-precision values. ### Inspecting a Vector’s Structure and Data [`count`](/documentation/Accelerate/DenseVector_Double/count) The number of items in the vector. [`data`](/documentation/Accelerate/DenseVector_Double/data) The array of double-precision, floating-point values. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)