CODEWITHSUNDEEP
juliaclassificationldamulticlass-classification
César Bertoni
César Bertoni

Reputation: 45

LDA on Julia using MultivariateStats

I'm learning classification methods using the book of Brunton & Kutz "Data-Driven Science and Engineering", but instead of use only the MATLAB and Python code resources, i rewriting the textbook examples using Julia, because is my main programming language.

I can't find why fitting a MulticlassLDA model to the data doesn't work, it returns a DimensionMismatch("Inconsistent array sizes."), but as far as i can tell my arrays are dispatched to the fit function as indicated in the documentation.

This is my code:

using MAT, LinearAlgebra, Statistics, MultivariateStats

# Load data in MATLAB format. Abailible in http://www.databookuw.com/

dogs = read(matopen("../DATA/dogData_w.mat"),"dog_wave") 
cats = read(matopen("../DATA/catData_w.mat"),"cat_wave")
    
CD = hcat(dogs,cats)

u, s, v = svd(CD .- mean(CD)) #SVD decomposition

xtrain = vcat(v[1:60,2:2:4],v[81:140,2:2:4])   #training data array, dims 120x2
label = Int.(vcat(ones(60),-ones(60)))         #label's vector, length 120
xtest = vcat(v[61:80,2:2:4],v[141:160,2:2:4])  

classf= fit(MulticlassLDA,2,xtrain,label)

Upvotes: 1

Views: 208

Answers (1)

Bogumił Kamiński
Bogumił Kamiński

Reputation: 69949

You have two issues which are fixed this way:

label = [fill(1, 60); fill(2, 60)] # labels must range from 1 to n
fit(MulticlassLDA,2,permutedims(xtrain),label) # observations in xtrain must be stored in columns (not rows)

See the comment in https://multivariatestatsjl.readthedocs.io/en/stable/index.html:

All methods implemented in this package adopt the column-major convention of JuliaStats: in a data matrix, each column corresponds to a sample/observation, while each row corresponds to a feature (variable or attribute).

And an explanation about y argument to fit https://multivariatestatsjl.readthedocs.io/en/stable/mclda.html#data-analysis:

y – the vector of class labels, of length n. Each element of y must be an integer between 1 and nc.

I hope this helps.

Upvotes: 1

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