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