Scientific Computing and Visualization Coding mathematics using Julia

Recall that using the Makie package, one can consider plotting the polynomial by creating a function that pulls out the coefficients. However, the Plots package has a related package called RecipesBase that allows one to create a plotting recipe. That is if p is a Polynomial, then we can write plot(p) and it will plot the polynomial. Let’s see how and don’t forget to add the package and then enter using RecipesBase.

The package RecipesBase includes the macro @recipe and although the documentation is sparse, this page is helpful in the background. The basic idea on a plot recipe is to do the following:

@recipe f(t::TheType,...)
end

where TheType is any datatype (either built-in or user defined). The recipe needs to return some number of vectors of points (depending on if it is 1D, 2D or a 3D plot). A simple version of this for type Polynomial is

@recipe function f(poly::Polynomial,xmin::Number=-2,xmax::Number=2)
xpts = LinRange(xmin,xmax,200)
ypts = map(x->eval(poly,x),xpts)
xpts,ypts
end

where line 2 creates an array of x values of length 200, then line 3 creates the y values for each x value. Line 4 returns a tuple of the pairs of points. We can now use this to plot a polynomial and we will need to using Plots to:

plot(poly1)

and since we defaulted the plot range from -2 to 2, we get the following plot: \begin{center} \pgfplotsset{scale=0.6} \plot{plots/comp-type/plot01.tex}{poly} \end{center}

and if we want to specify the plotting range:

 plot(poly1,0,4) 

we get