# Articles by Stéphane Laurent

### Expanding a polynomial with ‘caracas’, part 2

July 15, 2022 |

Last month, I posted an article showing a way to expand a polynomial in R when the coefficients of the polynomial contain some literal values, with the help of the caracas package. Today I wanted ... [Read more...]

### Slices of an implicit hypersurface with R

July 14, 2022 |

In a previous post, I showed how to draw a 3D slice of a 4D hypersurface when a parameterization of this hypersurface is available. Here we deal with the case when an implicit equation of the hypersurface... [Read more...]

### Search in a ‘DT’ table w/ or w/o a regular expression

July 2, 2022 |

It is possible to search in a ‘DT’ table with a regular expression: datatable( data = dat, options = list( search = list(regex = TRUE) ) ) But it could be desirable to have the possibility t... [Read more...]

### Pretty tooltips for ‘ggplot2’

July 2, 2022 |

Below is a simple example of a ‘ggplot2’ graphic with tooltips in a Shiny application. The tooltips are constructed with the help of the qTip2 JavaScript library. library(shiny) library(ggpl... [Read more...]

### Mapping a picture on a donut or a Hopf torus

June 29, 2022 |

The donut torus Given a number $$s \geqslant 1$$, the following map: $(u, v) \mapsto (x, y, z) = \frac{\Bigl(s\cos\frac{u}{s}, s\sin\frac{u}{s}, \sin v\Bigr)}{\sqrt{s^2+1}-\cos v}$ is ... [Read more...]

### On a Möbius transformation

June 20, 2022 |

Consider a complex number $$\gamma$$ such that $$|\gamma| __ 1$$ and the following matrix: $M = \begin{pmatrix} i & \gamma \\ \bar\gamma & -i \end{pmatrix}.$ ... [Read more...]

### Beautiful complex functions

June 19, 2022 |

I’ve just submitted a new package to CRAN: jacobi. It allows to evaluate the Jacobi theta functions as well as some related functions. In particular, some Eisenstein series, that you will see below. ... [Read more...]

### Scrollbar for the Shiny sidebar

June 16, 2022 |

It is easy to have a scrollbar for the sidebar of a Shiny app: one just has to use the CSS height: 90vh; overflow-y: auto;: library(shiny) library(shinyWidgets) ui [Read more...]

### SVG to PNG

June 16, 2022 |

Here is a way to get a high-quality PNG image with R: save it as SVG first, then convert the SVG file to a PNG file, with the rsvg package. Let’s see. I construct a hyperbolic Delaunay trian... [Read more...]

### Hopf torus, circle by circle

June 12, 2022 |

Remember my first post on the Hopf torus? I constructed it circle by circle. Below are some animations of this construction. I save the image each time a circle is added. The rgl package automatic... [Read more...]

### An example of the Minkowski addition

June 10, 2022 |

Now the MeshesOperations package can construct the Minkowski sum of two polyhedra, thanks to the C++ library CGAL and the R package RcppCGAL. Let’s see an example: the Minkowski sum of Leonardo da... [Read more...]

### Expanding a polynomial with ‘caracas’

June 6, 2022 |

I wanted to plot an algebraic isosurface with POV-Ray but the expression of the polynomial defining the isosurface was very long (the polynomial had degree 12). Moreover there was a square root in the coe... [Read more...]

### Update of ‘gyro’

June 3, 2022 |

I updated the gyro package (soon on CRAN). Here are the new features. Hyperbolic polyhedra in the Poincaré model The previous version of the package only dealt with hyperbolic ... [Read more...]

### Splitting RCGAL… and the connected components

May 26, 2022 |

I published two posts here about my package RCGAL, the first one about surface reconstruction, and the second one about Boolean operations on 3D meshes. Now I decided to spli... [Read more...]

### Hierarchical data visualization with Shiny and D3

May 19, 2022 |

I refreshed my old package 'dir2json' (5 years old). It uses a Haskell DLL and can only work on Windows. You can install it from Github: remotes::install_github("stla/dir2json") ... [Read more...]

### Animated multibarchart with (R)nvd3

May 19, 2022 |

I really like the animated multibarchart of the JavaScript library NVD3. That?s why I did the ?Rnvd3? package. library(Rnvd3) dat [Read more...]

### The ‘rAmCharts4’ package

May 14, 2022 |

My package rAmCharts4 has a moderate success on Github (twenty stars). So I decided to present it here. [Read more...]

### Boolean operations on meshes with R(CGAL)

May 13, 2022 |

I?m still working on my package RCGAL, that I already present in a previous post. This previous post was about the reconstruction of surfaces. Now I implemented the Boolean operations on mes... [Read more...]

### Copy ‘plotly’ image to the clipboard

March 15, 2022 |

The R code below shows how to get a “Copy to clipboard” button in the plotly toolbar. library(plotly) set.seed(666L) asd [Read more...]

### The E8 root polytope

March 13, 2022 |

The E8 root polytope, its vertices and its edges The E8 root polytope, also known as the $$4_{21}$$ polytope is a 8-dimensional polytope. The Cartesian coordinates of its vertices ar... [Read more...]
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