# init(x:yStart:yEnd:width:) Creates a rectangle mark with an y interval encoding and an x encoding. ``` nonisolated init(x: PlottableValue, yStart: PlottableValue, yEnd: PlottableValue, width: MarkDimension = .automatic) where X : Plottable, Y : Plottable ``` ## Parameters `x` The value plotted with y. `yStart` The value plotted with x start. `yEnd` The value plotted with x end. `width` The rectangle width. If `width` is not specified, then 70% of the step size will be used. If there is no step size a default width (in pts) will be used. ## Discussion ### Discussion Use this initializer to map the y start, y end and x position to a rectangle for each data element. Optionally, specify the width of the rectangles. The example below omits the optional `width` field and uses a number scale starting at (0,0) and ending at (6,6). The rectangle has the coordinates: (0,2), (0,4), (4,4), (4,2). ```swift Chart(data) { RectangleMark( yStart: .value("Rect yStart", 2), yEnd: .value("Rect yEnd", 4), x: .value("Rect X", 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)