How to add custom lines and areas in scatterplots

In the last panel of the  Annotate tab in step 3: Visualize, we can add extra lines and areas to our scatterplots. That's helpful if we want to add a rectangle around/behind certain data dots, or if we want to show a threshold line. 

For example, writing y=50 will create a horizontal line at the vertical axis point "50 years" (the same works for the horizontal axis, e.g. x=2000):

You can also define points, consisting of an x value and a y value, e.g. "2000, 50". If you define two points, a line will go from the first point to the second, e.g. "2000, 50, 4000, 70". Three or more points will define areas.

Styling

We can design these lines and areas. Here are all options that are available: 

@dashed Makes a dashed line
@dotted Makes a dotted line
@color:red / @color:#cc0000 Colors the line/area
@opacity:0.5 Makes the line/area more transparent (values between 0 and 1 are possible)
@stroke:red / @stroke:#cc0000 Creates and colors the stroke around an area
@width:2 Defines the width of the stroke around an area 

Try it out!

Here are examples you can copy & paste in the field. You might need to adjust the numbers, since your horizontal axis and vertical axis range might differ from the one in which we tried 

y = 50 Created a horizontal line that goes all the way through the chart on the height of y = 50.
x= 50 Created a vertical line that goes all the way through the chart on the height of x = 50.
2000, 50, 4000, 70 Creates a line that goes from the point 2000,50 to the point 4000, 70. 
0,0,0,5,5,5,5,0 @color:red @opacity:0.5 Creates a square, then set the color to red and make it half-transparent.
y = sin(x*20) @color:#1E4363  @width:2px Creates a sinus curve, make it blue and make the line a bit thicker. Functions like cos(x) and tan(x) are also supported.


💡 When working with data in date format, drawing lines by writing an equation such as "y = mx + c" doesn't work. Instead, you can draw a line by defining two points. For example, if you want to draw a straight line between (x, y) = (August 25 2020, 50) and (July 5 2020, 100), you can write: 25/08/2020, 50, 05/06/2020, 100 @color:gray

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