displease

The displease package provides non-linear interpolation between numeric values.

It is a replacement for seq() for when you want a sequence between two values which is not equally spaced.

Easing can look much better than strict linear interpolation when applied to objects moving spatially.

displease = displ + ease. The results are often used for animating visual displacement, and the non-linear interpolation is performed by applying an easing function.

Installation

You can install from GitHub with:

# install.package('remotes')
remotes::install_github('coolbutuseless/displease)

What’s in the box?

• seq_ease(x1, x2, n, type, direction) - create a sequence of length n between x1 and x2. Apply the easing function given by type.
• type is one of: sine, quad, cubic, quart, quint, exp, circle, back, elastic
• direction is one of: in, out, in-out

The following graph shows the seq_ease() output for n = 100 for all the different easing functions with given extents of x1 = 0 and x2 = 1

Example

library(displease)

# normal linear interpolation using seq()
(y_linear       <- seq(1, 10, length.out = 10))
#>  [1]  1  2  3  4  5  6  7  8  9 10

# Non-linear interpolation using {displease}
(y_cubic_in     <- seq_ease(1, 10, n=10, type = 'cubic', direction = 'in'))
#>  [1]  1.000000  1.012346  1.098765  1.333333  1.790123  2.543210  3.666667
#>  [8]  5.234568  7.320988 10.000000
(y_cubic_in_out <- seq_ease(1, 10, n=10, type = 'cubic', direction = 'in-out'))
#>  [1]  1.000000  1.049383  1.395062  2.333333  4.160494  6.839506  8.666667
#>  [8]  9.604938  9.950617 10.000000

plot(1:10, y_linear      , type = 'b')

plot(1:10, y_cubic_in    , type = 'b')

plot(1:10, y_cubic_in_out, type = 'b')

Animated example

This animation shows each of the easing types.

Related Software

• tweenr is a more general purpose package for interpolation