The FourierDescriptors Package

[This article was first published on John Myles White » Statistics, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

Introduction

I’ve just uploaded a new package to CRAN based on a stimulus generation algorithm that I use for my experiments on vision. The FourierDescriptors package provides methods for creating, manipulating and visualizing Fourier descriptors, which are a representational scheme used to describe closed planar contours. The canonical reference from the literature is Zahn and Roskies 1972. The images most easily described using Fourier descriptors are useful as stimuli for experiments in psychology and neuroscience.

Installation

This package has been submitted to CRAN. When it propagates through the mirrors, you can install it using a simple call to install.packages():

1
install.packages('FourierDescriptors')

For the time being, please install it using the included source package by downloading the GitHub repository and running:

1
R CMD INSTALL FourierDescriptors_*.tar.gz

Basic Usage Example

The following example showcases the central methods that currently exist in the FourierDescriptors package:

1
2
3
4
5
6
7
8
library('FourierDescriptors')
 
fd1 <- create.fourier.descriptor()
print(fd1)
plot(fd1)
 
fd2 <- random.fourier.descriptor(32, 2)
plot(fd2)

Gaining Intuition about the Amplitude Spectrum

It’s useful to see the images generated by very basic amplitude spectra to see how these determine the shape of the induced contour.

1
2
library('FourierDescriptors')
plot(create.fourier.descriptor(amplitude = c(0, 0, 0, 0)))
image1.png
1
plot(create.fourier.descriptor(amplitude = c(0, 1, 0, 0)))
image2.png
1
plot(create.fourier.descriptor(amplitude = c(0, 0, 0, 1)))
image3.png
1
plot(create.fourier.descriptor(amplitude = c(0, 1, 0, 1)))
image4.png
1
2
3
4
plot(random.fourier.descriptor(24,
                               non.zero.frequencies = 4,
                               generating.function = function() {runif(1)}),
     steps = 360 * 10)
image5.png

Please note that only even-numbered frequencies can have non-zero amplitudes or the described curve will not be closed.

To leave a comment for the author, please follow the link and comment on their blog: John Myles White » Statistics.

R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

Never miss an update!
Subscribe to R-bloggers to receive
e-mails with the latest R posts.
(You will not see this message again.)

Click here to close (This popup will not appear again)