Point Markers on Line Charts

What chm Draws on a Line Chart

The point marker form of chm is chm=<shape>,<color>,<series_index>,<which_points>,<size>, and several groups are joined with |.

• shape is one of the five letters in the table below.
• color is a hex colour written without a leading #. It fills the whole marker, which is drawn as a solid shape with no separate outline.
• series_index picks the series the markers go on, counting from 0.
• which_points has to be -1, meaning every point of that series. Image-Charts does not draw markers on a subset of the points, and a group that asks for one is dropped, so the series comes back with no markers on it at all.
• size is the diameter of the marker in pixels, so 12 draws a marker six pixels from its centre to its edge.

Markers on One Series

Markers are usually worth adding when the reader has to read individual values off the chart rather than follow a trend. One group is enough, and the marker colour is independent of the line colour set by chco, which is how you make the points stand out against their own line.

https://image-charts.com/chart?cht=lc&chd=a:31,42,38,55,61,58,72&chco=1F3B99&chls=3&chm=o,E8622A,0,-1,16&chs=700x260&chxt=x,y

The Other Things chm Does

chm is also the parameter that fills the area under a line, that draws a tracking line across a bar chart and that prints the data values next to each point. Those forms take different arguments in the same group.

• b and B fill the area under a line, taking a colour and the indices of the lines to fill between.
• D draws one series as a line over a bar chart, which is how you overlay a trend on top of bars.
• N prints the value of each point as text, with an optional format string for currency, decimals and thousand separators.

The optional z-order field that Google documented after size is accepted and ignored, and the arrow and line prefixes it allowed have no Image-Charts equivalent. The reference documentation gives the full grammar of each form.