Hi all,


Thank you tableau. We now have dashed lines in 2023.2 meaning a new way of using the functionality to draw attention to specific parts of our charts.

Now, early disclaimer. I will leave the when to use / how and why to others. There are plenty of better advocates for best practice in the community and resources at your finger tips of when to use dashs in your charts. In fact, just this week the Flerlage Twins released this fantastic blog on just that.  It really dives into some great examples around projections, confidence intervals as well as the different activity of lines vs colour. Please check it out here!

If you want to put your new dot lines in 2023.2 to good use, why not also have a go at the latest weeks Workout Wednesday.

Anyway, for the blog this week we will look at what it means for the maths behind radial and curved designs, and the improvements it can bring.

What it was before when looking at radials?

Before the introduction of dashed lines we could create a similar effect through data scaffolding.

You can check out how chord / arc charts we could create dashed effects using an extra column onto detail. This help essentially ‘cut up’ our data densification points splitting them out. Here’s where i’ve done it before.

But what you may notice with these dashed lines are they are of different lengths.

It was previously only in the case of perfect circles that the length of each fake dash would be of equal length. Which makes sense when we are essentially marking where we want our points along a curve, they won’t all be equidistance if our lines start spiralling here there and everywhere.

Below you can see how they work fine for radials, where I’ve used them in a champions league visual, years ago. (Extra time had a radial of certain length vs going to penalties….)

Mathematically this became problematic for non-circles because we want a point because we need our line to curve and not be jagged, but we don’t want the point because it makes for unequal length arc dots.

Tough, which meant previously unless looking at circles it was kind of a design no go.

New 2023.2 Update

The good news is, that problem is no more.

Opening up that old Bezier curve work I had created, I can go back in and remove the detail and change the line to dashes very easily. It is under path and Line Pattern!

By all means take a copy of the dashboard and do the same.

Let’s See It In Practice From Scratch

Lets go from the very beginning.

Connect to a dataset with 100 rows (Column Name: T)

  • Create a field Rank, with the value T in it.
  • Create and Angle field with 360/100
    (This is the a full circle / the number of points, each angle should be the same gap)
  • Create a rank angle calculation (rank * angle)
    This creates the spread of each mark to be along the curve.
  • Create x field, This is cos(radians(rankangle))
  • Create y field, This is sin(radians(rankangle))
    x and y is following trigonometry to create the waves that together make a circle.
  • Plot them against one another to see how they interact and make the new mark line of the path a dash. You can download my example workbook from my page here.

Not the most creative design or curves, but its a good way of showcasing the even ‘spacing’ of the dots from the dashed line ability.

This is regardless of our data scaffolding bunching that you see, if we change our marks card back to circles it now doesnt matter that they no longer are equidistant.

We can also check this works using the old workbook on my profile, here are a few examples using arcs

and chord diagrams.

We can even dual axis two lines against one another to have some of our lines as dashes and others as straight lines.

Are There Any Good Examples Online?

Well it jogged my memory of when I was putting together my iron Viz Feeder for 2022, and the inspiration I found in this beatles visual. You can find a copy on designinspo.

If you are after alternative creative ways of using dashes that isn’t radial inspired, then I’ve also seen Dennis doing some stuff with it implemented in maps – with some amazing user cases including pedestrian/bike paths, park trails, restricted roads, planned roads, disputed boundaries.

Excited to see how people utilise it in creative ways.

Speak soon – time for a morning run!