Contours
A Contour object is used to draw a contour line. It takes a multivariate function and a threshold level:
layout:
OneGraph:
graph:
objects:
- Contour:
level: 16
fn: "(x)*(y)"
- Label:
coordinates: [4,4]
text: x \times y = 16
color: grey
You can either define a threshold level directly, or via a point. For example, the following code draws a contour line for f(x,y) = f(4,4):
layout:
OneGraph:
graph:
objects:
- Contour:
coordinates: [4,4]
fn: "(x)*(y)"
- Point:
coordinates: [4,4]
droplines:
vertical:
horizontal:
- Label:
coordinates: [2,8]
text: x \times y = 4 \times 4
color: grey
Contour lines are grey by default, with a strokeWidth of 1. You can change the color of the contour line itself using the color or stroke attribute. You can shade the areas above and below the contour line by specifying colors in the fillAbove and fillBelow attributes:
layout:
OneGraph:
graph:
objects:
- Contour:
level: 16
fn: "(x)*(y)"
color: blue
fillAbove: green
fillBelow: red
- Label:
coordinates: [8,8]
text: x \times y > 16
color: green
bgcolor: none
- Label:
coordinates: [2,2]
text: x \times y < 16
color: red
bgcolor: none
A ContourMap object takes a function and an array of levels and generates the contours for them. By default, it makes the contour lines thinner (0.5px rather than 1px):
layout:
OneGraph:
graph:
objects:
- ContourMap:
levels: [1, 4, 9, 16, 25, 36, 49, 64, 81]
fn: "(x)*(y)"