Adjust the number of grid lines in a SwiftUI Chart

February 12, 2023

I am trying to adjust (reduce) the number of gridlines in my SwiftUI Chart.

I have the following code:

Chart() {
    ForEach(self.viewModel.downloadHistory) { item in
        LineMark(x: .value(String.empty, item.timestamp), y: .value(String.empty, item.value.floatValue))
            .interpolationMethod(.stepCenter)
            .foregroundStyle(Colors.download)
    }
}
.chartXAxis(.hidden)
.frame(height: 64.0)
.gridColumnAlignment(.center)
.chartYAxis() {
    AxisMarks() { value in
        AxisGridLine(centered: true, stroke: StrokeStyle(dash: [4.0, 4.0]))
        AxisValueLabel()
        {
            if let value = value.as(UInt64.self)
            {
                Text(DiskUtilities.toSpeedNoComma(value))
            }
        }
    }
}
.padding()

This results in the following chart:

I like the design, however, I would like to:

Either reduce the number of gridlines.
Or only show the text at the 0%, 50% and 100% line. Is this possible?

Is either of those two options possible?

>Solution :

AxisMarks has various initializers that take parameters. The parameter you’re interested in is values, which can be either AxisMarkValues or an array of some Plottable.

Try AxisMarkValues.automatic(desiredCount: 3).