#Line plot series

Typically z is a categorical value such as a series name. If the z channel is specified, data is grouped by z to form separate series. z - a categorical value to group data into seriesīy default, the data is assumed to represent a single series (a single value that varies over time, e.g.).In addition to the standard mark options, the following optional channels are supported: y - the vertical position bound to the y scale.x - the horizontal position bound to the x scale.A step curve is nice for emphasizing when the value changes, while basis and catmull–rom are nice for smoothing. The default curve is linear, which draws straight line segments between pairs of adjacent points. Interpolation is controlled by the curve option.

Setting z to null forces a single line we want the stroke to vary within the line instead of producing a separate line for each color. For example, below we plot the a 14-day moving average of the daily highs and lows in temperate San Francisco using the window transform.

While more verbose, this allows you to choose different options for each line. The sort transform above places the red lines on top of the gray ones to improve readability.Īs an alternative to z, you can render multiple lines using multiple marks. When using z, lines are drawn in input order.