# init(xStart:xEnd:y:height:) Creates a rectangle mark with a fixed x interval and y encoding. ``` nonisolated init(xStart: CGFloat? = nil, xEnd: CGFloat? = nil, y: PlottableValue, height: MarkDimension = .automatic) where Y : Plottable ``` ## Discussion - xStart: The x start position. If `xStart` is `nil` then the rectangle will start at the leading edge of the plotting area. - xEnd: The x end position. If `xEnd` is `nil` then the rectangle will end at the trailing edge of the plotting area. - y: The value plotted with y. - height: The rectangle height. If `height` is not specified, then 70% of the step size will be used. If there is no step size a default height (in pts) will be used. ### Discussion Use this initializer to map a y position to a rectangle for each data element. Optionally, specify the height, xStart position, or xEnd position, of the rectangles. The example below omits the optional `x`, `width`, and `height` parameters and uses a number scale starting at (0,0) and ending at (6,6). The rectangle has the coordinates: (0,0), (0,3), (6,3), (6,0). ```swift Chart(data) { RectangleMark( y: .value("Rect Y", 3) ) .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)