generate_shifted_axis: Generate a dataframe and geoms to add an auxiliary axis to a...

In einGlasRotwein/ForBioPsy: File Administration and Data Preprocessing for the BioPsy group

Description

Generate a dataframe and geoms to add an auxiliary axis to a plot

Usage

generate_shifted_axis(limits, steps, other_ax_steps, axis, tick_sz = 0.7,
  intercept = 0)

Arguments

limits	A vector with two elements defining the limits of your axis.
steps	A single integer or double specifying how far the ticks of the new auxiliary axis should be apart, in the unit of the axis.
other_ax_steps	A single integer or double specifying the how far the ticks of the orthogonal axis are apart, in the unit of the orthogonal axis. Is used to determine the size of the ticks. See details.
axis	A character indicating which axis should be generated. Can be set to "x" or "y".
tick_sz	Determines the size of the ticks, which is expressed as percentage of the other axis's steps. Defaults to .7. See details.
intercept	A single integer or double specifying where the new auxiliary axis should cross the orthogonal axis, in units of the orthogonal axis. Defaults to 0.

Details

The main output of the function is a dataframe that contains all the information needed to build an auxiliary axis with tick marks for your plot which cross the orthogonal axis at a specified intercept. Simultaneously, generate_shifted_axis() will print the code you need to add to your plot to insert your newly created auxiliary axis. Note that you need to replace 'YOURDF' with the name of the object you saved the function's output to.

As you can tell from this printed output, it is not a true axis that is created, but instead a combination of geom_hline (or geom_vline) and geom_segment to mimic an axis. You may want to add theme(axis.line = element_blank()) or even theme(axis.line = element_blank(), axis.ticks = element_blank()) to your plot to get rid of the usual axis lines.

Note that the axis text is not shifted, but stays with the actual axis, because the function is optimised for readable EEG plots. See the example folder on GitHub.

As the ticks are in fact plotted with x and y coordinates, the tick size is computed relative to the size of the steps you auxiliary axis is orthogonal to. That is, if you are creating a y-axis, the ticks of your x-axis are spaced 200 units apart and tick_sz is set to 1, the ticks will be exactly as long as the space between two ticks of the x-axis.

Currently, this generate_shifted_axis() assumes that both of your axes are numerical and is at an experimental stage. Feeding it with anything that widely differs from plots roughly resembling an EEG data plot or twisting the limits so they don't correspond to your plot's actual parameters may lead to quirky results.

Author(s)

Juliane Tkotz [e-mail]

Examples

x_ticks <- generate_shifted_axis(
  c(-200, 1100), 200, 1, "x"
  )

einGlasRotwein/ForBioPsy documentation built on Nov. 4, 2019, 11:49 a.m.