Generating Synthetic Data
Here synthetic data means artificially generated data, with no reference to a "real world" data set. Not to be confused "fake data" obtained by resampling from a distribution fit to some actual real data.
MLJ has a set of functions - make_blobs, make_circles, make_moons and make_regression (closely resembling functions in scikit-learn of the same name) - for generating synthetic data sets. These are useful for testing machine learning models (e.g., testing user-defined composite models; see Composing Models)
Generating Gaussian blobs
MLJBase.make_blobs — Function
X, y = make_blobs(n=100, p=2; kwargs...)Generate Gaussian blobs for clustering and classification problems.
Return value
By default, a table X with p columns (features) and n rows (observations), together with a corresponding vector of n Multiclass target observations y, indicating blob membership.
Keyword arguments
shuffle=true: whether to shuffle the resulting points,centers=3: either a number of centers or ac x pmatrix withcpre-determined centers,cluster_std=1.0: the standard deviation(s) of each blob,center_box=(-10. => 10.): the limits of thep-dimensional cube within which the cluster centers are drawn if they are not provided,eltype=Float64: machine type of points (any subtype ofAbstractFloat).rng=Random.GLOBAL_RNG: anyAbstractRNGobject, or integer to seed aMersenneTwister(for reproducibility).as_table=true: whether to return the points as a table (true) or a matrix (false). Iffalsethe targetyhas integer element type.
Example
X, y = make_blobs(100, 3; centers=2, cluster_std=[1.0, 3.0])using MLJ, DataFrames
X, y = make_blobs(100, 3; centers=2, cluster_std=[1.0, 3.0])
dfBlobs = DataFrame(X)
dfBlobs.y = y
first(dfBlobs, 3)| Row | x1 | x2 | x3 | y |
|---|---|---|---|---|
| Float64 | Float64 | Float64 | Cat… | |
| 1 | -9.22474 | 3.59473 | -4.85365 | 1 |
| 2 | -8.22333 | 1.80851 | -3.2737 | 1 |
| 3 | 4.73705 | -2.32696 | -2.87838 | 2 |
using VegaLite
dfBlobs |> @vlplot(:point, x=:x1, y=:x2, color = :"y:n") dfBlobs |> @vlplot(:point, x=:x1, y=:x3, color = :"y:n") Generating concentric circles
MLJBase.make_circles — Function
X, y = make_circles(n=100; kwargs...)Generate n labeled points close to two concentric circles for classification and clustering models.
Return value
By default, a table X with 2 columns and n rows (observations), together with a corresponding vector of n Multiclass target observations y. The target is either 0 or 1, corresponding to membership to the smaller or larger circle, respectively.
Keyword arguments
shuffle=true: whether to shuffle the resulting points,noise=0: standard deviation of the Gaussian noise added to the data,factor=0.8: ratio of the smaller radius over the larger one,eltype=Float64: machine type of points (any subtype ofAbstractFloat).rng=Random.GLOBAL_RNG: anyAbstractRNGobject, or integer to seed aMersenneTwister(for reproducibility).as_table=true: whether to return the points as a table (true) or a matrix (false). Iffalsethe targetyhas integer element type.
Example
X, y = make_circles(100; noise=0.5, factor=0.3)using MLJ, DataFrames
X, y = make_circles(100; noise=0.05, factor=0.3)
dfCircles = DataFrame(X)
dfCircles.y = y
first(dfCircles, 3)| Row | x1 | x2 | y |
|---|---|---|---|
| Float64 | Float64 | Cat… | |
| 1 | -0.34498 | 0.96241 | 1 |
| 2 | -0.85398 | -0.522635 | 1 |
| 3 | -1.02128 | -0.178872 | 1 |
using VegaLite
dfCircles |> @vlplot(:circle, x=:x1, y=:x2, color = :"y:n") Sampling from two interleaved half-circles
MLJBase.make_moons — Function
make_moons(n::Int=100; kwargs...)Generates labeled two-dimensional points lying close to two interleaved semi-circles, for use with classification and clustering models.
Return value
By default, a table X with 2 columns and n rows (observations), together with a corresponding vector of n Multiclass target observations y. The target is either 0 or 1, corresponding to membership to the left or right semi-circle.
Keyword arguments
shuffle=true: whether to shuffle the resulting points,noise=0.1: standard deviation of the Gaussian noise added to the data,xshift=1.0: horizontal translation of the second center with respect to the first one.yshift=0.3: vertical translation of the second center with respect to the first one.eltype=Float64: machine type of points (any subtype ofAbstractFloat).rng=Random.GLOBAL_RNG: anyAbstractRNGobject, or integer to seed aMersenneTwister(for reproducibility).as_table=true: whether to return the points as a table (true) or a matrix (false). Iffalsethe targetyhas integer element type.
Example
X, y = make_moons(100; noise=0.5)using MLJ, DataFrames
X, y = make_moons(100; noise=0.05)
dfHalfCircles = DataFrame(X)
dfHalfCircles.y = y
first(dfHalfCircles, 3)| Row | x1 | x2 | y |
|---|---|---|---|
| Float64 | Float64 | Cat… | |
| 1 | -0.994062 | 0.325009 | 0 |
| 2 | 0.83938 | 0.488552 | 0 |
| 3 | -0.768367 | 0.578792 | 0 |
using VegaLite
dfHalfCircles |> @vlplot(:circle, x=:x1, y=:x2, color = :"y:n") Regression data generated from noisy linear models
MLJBase.make_regression — Function
make_regression(n, p; kwargs...)Generate Gaussian input features and a linear response with Gaussian noise, for use with regression models.
Return value
By default, a tuple (X, y) where table X has p columns and n rows (observations), together with a corresponding vector of n Continuous target observations y.
Keywords
intercept=true: Whether to generate data from a model with intercept.n_targets=1: Number of columns in the target.sparse=0: Proportion of the generating weight vector that is sparse.noise=0.1: Standard deviation of the Gaussian noise added to the response (target).outliers=0: Proportion of the response vector to make as outliers by adding a random quantity with high variance. (Only applied ifbinaryisfalse.)as_table=true: WhetherX(andy, ifn_targets > 1) should be a table or a matrix.eltype=Float64: Element type forXandy. Must subtypeAbstractFloat.binary=false: Whether the target should be binarized (via a sigmoid).eltype=Float64: machine type of points (any subtype ofAbstractFloat).rng=Random.GLOBAL_RNG: anyAbstractRNGobject, or integer to seed aMersenneTwister(for reproducibility).as_table=true: whether to return the points as a table (true) or a matrix (false).
Example
X, y = make_regression(100, 5; noise=0.5, sparse=0.2, outliers=0.1)using MLJ, DataFrames
X, y = make_regression(100, 5; noise=0.5, sparse=0.2, outliers=0.1)
dfRegression = DataFrame(X)
dfRegression.y = y
first(dfRegression, 3)| Row | x1 | x2 | x3 | x4 | x5 | y |
|---|---|---|---|---|---|---|
| Float64 | Float64 | Float64 | Float64 | Float64 | Float64 | |
| 1 | -0.518246 | -0.79514 | 1.37822 | 0.969101 | 0.0807837 | -0.0888481 |
| 2 | -2.01576 | 0.312555 | -1.09316 | 0.40927 | -0.668211 | -1.63218 |
| 3 | -0.275527 | -0.0712012 | -0.350757 | -1.07003 | 0.474841 | 0.833761 |