# init(x:y:t:domain:function:) Creates a mark that graphs a parametric function (x, y) = f(t). ``` nonisolated init(x: Text, y: Text, t: Text, domain: ClosedRange, function: @escaping @Sendable (Double) -> (x: Double, y: Double)) ``` ## Discussion Parameters: - x: The localized string key for the x label. - y: The localized string key for the y label. - t: The localized string key for the t label. - domain: The domain of t. Must be a finite domain. - function: The function to graph. Returns a tuple of (x, y) for a value of t. > Note: For t values where the function is undefined or is infinity, the function is expected to return `Double.nan` or `Double.infinity` respectively. --- 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)