The X axis or category axis. Normally this is the horizontal axis, though if the chart is inverted this is the vertical axis. In case of multiple axes, the xAxis node is an array of configuration objects. See the Axis class for programmatic access to the axis.
Arguments defined in https://api.highcharts.com/highcharts/xAxis.
In Highmaps, the axis is hidden, but it is used behind the scenes to control features like zooming and panning. Zooming is in effect the same as setting the extremes of one of the exes.
highchart() %>% hc_add_series( data = c(7.0, 6.9, 9.5, 14.5, 18.2, 21.5, 25.2, 26.5, 23.3, 18.3, 13.9, 9.6), type = "spline" ) %>% hc_xAxis( title = list(text = "x Axis at top"), alternateGridColor = "#FDFFD5", opposite = TRUE, plotLines = list( list( label = list(text = "This is a plotLine"), color = "#FF0000", width = 2, value = 5.5 ) ) )