# init(xStart:xEnd:yStart:yEnd:) Creates a rectangle mark with an x interval encoding and a fixed y interval. ``` nonisolated init(xStart: PlottableValue, xEnd: PlottableValue, yStart: CGFloat? = nil, yEnd: CGFloat? = nil) where X : Plottable ``` ## Discussion - xStart: The value plotted with x start. - xEnd: The value plotted with x end. - yStart: The y end position. If `yStart` is `nil` then the rectangle will start at the leading edge of the plotting area. - yEnd: The y end position. If `yEnd` is `nil` then the rectangle will end at the trailing edge of the plotting area. ### Discussion Use this initializer to map the x start and x end to a rectangle for each data element. Optionally, specify the yStart or yEnd position of the rectangles. The example below omits the optional `y` and `height` fields and uses a number scale starting at (0,0) and ending at (6,6). The rectangle has the coordinates: (2,0), (2,6), (4,6), (4,0). ```swift Chart(data) { RectangleMark( xStart: .value("Rect xStart", 2), xEnd: .value("Rect xEnd", 4) ) .opacity(0.2) PointMark( x: .value("X", $0.x), y: .value("Y", $0.y) ) } ```  --- 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)