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Asked by FIR
on 17 Apr 2012

hi can anyone tell how to implement c4.5 algorithm plz for fisheris data ,is there any code for it

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Answer by Ilya
on 17 Apr 2012

Statistics Toolbox provides a decision tree implementation based on the book Classification and Regression Trees by Breiman et al (CART). If you have MATLAB 11a or later, do 'doc ClassificationTree' and 'doc RegressionTree'. If you have an older version, do 'doc classregtree'.

The CART algorithm is different from C4.5.

FIR
on 18 Apr 2012

But Illaya how to process c4.5 then can i use t = classregtree(X,y) for c4.5

Ilya
on 18 Apr 2012

I don't understand your question. Try asking it again using proper grammar.

FIR
on 19 Apr 2012

u said c4.5 is different from cart,can i use calssregtree for c4.5 classification

second question is

i get error

Error using classperf (line 244)

When class labels of the CP object is a cell array of strings and

the classifier output is a numeric array, it must contain valid

indices of the class labels or NaNs for inconclusive results.

i posted this question many times but i did not get reply please answer

Answer by Ilya
on 19 Apr 2012

I don't know if you can use classregtree for "c4.5 classification". If you are looking for **a** decision tree implementation, you can use classregtree. If you are looking specifically for **the** C4.5 algorithm, obviously you cannot use classregtree. If you don't know enough to choose one algorithm over the other, perhaps you should use whatever is readily available, that is, classregtree.

I am not going to answer your 2nd question in this thread. I'll note however that the error message gives you a clue. classperf expects class indices, and you are giving it what exactly?

Answer by Muhammad Aasem
on 25 May 2012

I found the following source code for C4.5 algorithm. I hope it works for you:

function test_targets = C4_5(train_patterns, train_targets, test_patterns, inc_node)

% Classify using Quinlan's C4.5 algorithm % Inputs: % training_patterns - Train patterns % training_targets - Train targets % test_patterns - Test patterns % inc_node - Percentage of incorrectly assigned samples at a node % % Outputs % test_targets - Predicted targets

%NOTE: In this implementation it is assumed that a pattern vector with fewer than 10 unique values (the parameter Nu) %is discrete, and will be treated as such. Other vectors will be treated as continuous

[Ni, M] = size(train_patterns); inc_node = inc_node*M/100; Nu = 10;

%Find which of the input patterns are discrete, and discretisize the corresponding %dimension on the test patterns discrete_dim = zeros(1,Ni); for i = 1:Ni, Ub = unique(train_patterns(i,:)); Nb = length(Ub); if (Nb <= Nu), %This is a discrete pattern discrete_dim(i) = Nb; dist = abs(ones(Nb ,1)*test_patterns(i,:) - Ub'*ones(1, size(test_patterns,2))); [m, in] = min(dist); test_patterns(i,:) = Ub(in); end end

%Build the tree recursively disp('Building tree') tree = make_tree(train_patterns, train_targets, inc_node, discrete_dim, max(discrete_dim), 0);

%Classify test samples disp('Classify test samples using the tree') test_targets = use_tree(test_patterns, 1:size(test_patterns,2), tree, discrete_dim, unique(train_targets));

%END

function targets = use_tree(patterns, indices, tree, discrete_dim, Uc) %Classify recursively using a tree

targets = zeros(1, size(patterns,2));

if (tree.dim == 0) %Reached the end of the tree targets(indices) = tree.child; return end

%This is not the last level of the tree, so: %First, find the dimension we are to work on dim = tree.dim; dims= 1:size(patterns,1);

%And classify according to it if (discrete_dim(dim) == 0), %Continuous pattern in = indices(find(patterns(dim, indices) <= tree.split_loc)); targets = targets + use_tree(patterns(dims, :), in, tree.child(1), discrete_dim(dims), Uc); in = indices(find(patterns(dim, indices) > tree.split_loc)); targets = targets + use_tree(patterns(dims, :), in, tree.child(2), discrete_dim(dims), Uc); else %Discrete pattern Uf = unique(patterns(dim,:)); for i = 1:length(Uf), if any(Uf(i) == tree.Nf) %Has this sort of data appeared before? If not, do nothing in = indices(find(patterns(dim, indices) == Uf(i))); targets = targets + use_tree(patterns(dims, :), in, tree.child(find(Uf(i)==tree.Nf)), discrete_dim(dims), Uc); end end end

%END use_tree

function tree = make_tree(patterns, targets, inc_node, discrete_dim, maxNbin, base) %Build a tree recursively

[Ni, L] = size(patterns); Uc = unique(targets); tree.dim = 0; %tree.child(1:maxNbin) = zeros(1,maxNbin); tree.split_loc = inf;

if isempty(patterns), return end

%When to stop: If the dimension is one or the number of examples is small if ((inc_node > L) | (L == 1) | (length(Uc) == 1)), H = hist(targets, length(Uc)); [m, largest] = max(H); tree.Nf = []; tree.split_loc = []; tree.child = Uc(largest); return end

%Compute the node's I for i = 1:length(Uc), Pnode(i) = length(find(targets == Uc(i))) / L; end Inode = -sum(Pnode.*log(Pnode)/log(2));

%For each dimension, compute the gain ratio impurity %This is done separately for discrete and continuous patterns delta_Ib = zeros(1, Ni); split_loc = ones(1, Ni)*inf;

for i = 1:Ni, data = patterns(i,:); Ud = unique(data); Nbins = length(Ud); if (discrete_dim(i)), %This is a discrete pattern P = zeros(length(Uc), Nbins); for j = 1:length(Uc), for k = 1:Nbins, indices = find((targets == Uc(j)) & (patterns(i,:) == Ud(k))); P(j,k) = length(indices); end end Pk = sum(P); P = P/L; Pk = Pk/sum(Pk); info = sum(-P.*log(eps+P)/log(2)); delta_Ib(i) = (Inode-sum(Pk.*info))/-sum(Pk.*log(eps+Pk)/log(2)); else %This is a continuous pattern P = zeros(length(Uc), 2);

%Sort the patterns [sorted_data, indices] = sort(data); sorted_targets = targets(indices);

%Calculate the information for each possible split I = zeros(1, L-1); for j = 1:L-1, %for k =1:length(Uc), % P(k,1) = sum(sorted_targets(1:j) == Uc(k)); % P(k,2) = sum(sorted_targets(j+1:end) == Uc(k)); %end P(:, 1) = hist(sorted_targets(1:j) , Uc); P(:, 2) = hist(sorted_targets(j+1:end) , Uc); Ps = sum(P)/L; P = P/L;

Pk = sum(P); P1 = repmat(Pk, length(Uc), 1); P1 = P1 + eps*(P1==0);

info = sum(-P.*log(eps+P./P1)/log(2)); I(j) = Inode - sum(info.*Ps); end [delta_Ib(i), s] = max(I); split_loc(i) = sorted_data(s); end end

%Find the dimension minimizing delta_Ib [m, dim] = max(delta_Ib); dims = 1:Ni; tree.dim = dim;

%Split along the 'dim' dimension Nf = unique(patterns(dim,:)); Nbins = length(Nf); tree.Nf = Nf; tree.split_loc = split_loc(dim);

%If only one value remains for this pattern, one cannot split it. if (Nbins == 1) H = hist(targets, length(Uc)); [m, largest] = max(H); tree.Nf = []; tree.split_loc = []; tree.child = Uc(largest); return end

if (discrete_dim(dim)), %Discrete pattern for i = 1:Nbins, indices = find(patterns(dim, :) == Nf(i)); tree.child(i) = make_tree(patterns(dims, indices), targets(indices), inc_node, discrete_dim(dims), maxNbin, base); end else %Continuous pattern indices1 = find(patterns(dim,:) <= split_loc(dim)); indices2 = find(patterns(dim,:) > split_loc(dim)); if ~(isempty(indices1) | isempty(indices2)) tree.child(1) = make_tree(patterns(dims, indices1), targets(indices1), inc_node, discrete_dim(dims), maxNbin, base+1); tree.child(2) = make_tree(patterns(dims, indices2), targets(indices2), inc_node, discrete_dim(dims), maxNbin, base+1); else H = hist(targets, length(Uc)); [m, largest] = max(H); tree.child = Uc(largest); tree.dim = 0; end end

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