Added function generate_twospirals from matlab

Author: Sergiorezende22

src/matlab.jl

@@ -0,0 +1,30 @@
+"""
+    generate_twospirals(;    n_samples::Int = 2000,
+                             start_degrees::Int = 90,
+                             total_degrees::Int = 570,
+                             noise::Float64 = 0.2
+Generate two spirals dataset. Return a Nx3 matrix, where each line contains the X,Y coordinates and the class of an instance.
+# Arguments
+- `n_samples::Int = 2000`: The total number of points generated.
+- `start_degrees::Int = 90`: Determines how far from the origin the spirals start.
+- `total_degrees::Int = 570`: Controls the lenght of the spirals.
+- `noise::Float64 = 0.2`: Determines the noise in the dataset.
+Reference: [link](https://la.mathworks.com/matlabcentral/fileexchange/41459-6-functions-for-generating-artificial-datasets)
+"""
+function generate_twospirals(; n_samples::Int = 2000,
+                               start_degrees::Int = 90,
+                               total_degrees::Int = 570,
+                               noise::Float64 = 0.2)
+   start_degrees = deg2rad(start_degrees);
+
+   N1 = floor(Int, n_samples / 2);
+   N2 = n_samples - N1;
+
+   n = start_degrees .+ sqrt.(rand(N1,1)) .* deg2rad(total_degrees);
+   d1 = [-cos.(n).*n + rand(N1,1).*noise sin.(n).*n+rand(N1,1).*noise zeros(N1,1)];
+
+   n = start_degrees .+ sqrt.(rand(N2,1)) .* deg2rad(total_degrees);
+   d2 = [cos.(n).*n+rand(N2,1)*noise -sin.(n).*n+rand(N2,1)*noise ones(N2,1)];
+
+   return [d1; d2];
+end