I execute the following program and none of the variables in the decision tree function and below show up in the workspace? Am I doing something wrong with how I'm defining and using the functions?

load iris.dat

%discretizeData

discretizedData = zeros(150,5);
for i = 1:size(iris,2)
    currentColumn = iris(:,i);
    bins = length(currentColumn)/4;
    discretizedData(:,i) = round(currentColumn/bins)+1;
    if(i == 5)
       for j = 1: size(iris,1)
          if( iris(j,5) == 2 || iris(j,5) == 3)
              discretizedData(j,5) = -1;
          end
       end
    end
end

%generate test and train data

posIndex = randperm(50,25);
negIndex = randperm(150,50);

trainData = zeros(75,5);
trainData(1:25,:) = discretizedData(posIndex,:);
trainData(26:75,:) = discretizedData(negIndex,:);

list1=[];
list2=[];

%start of the decision tree algorithm
function e = dctree(trainData,list,dominant)
    if size(trainData,1) == 0
        list(length(list)+1) = strcat('=>',num2str(dominant));
        disp(list); %print the rule at the leaf
        e = 1;
    end
    dominant = dominantLabel(trainData);
    nFeatures = size(trainData,2)-1;
    levelEntropy = 999;
    for i = 1:nFeatures
        uniqueValues = unique(trainData(:,i));
        nUnique = length(uniqueValues);
        for u = 1:nUnique
            tposExample = trainData((find(trainData(:,i) == uniqueValues(u) & trainData(:,5) == 1)),:);
            tnegExample = trainData((find(trainData(:,i) == uniqueValues(u) & trainData(:,5) == -1)),:);
            fposExample = trainData((find(trainData(:,i) ~= uniqueValues(u) & trainData(:,5) == 1)),:);
            fnegExample = trainData((find(trainData(:,i) ~= uniqueValues(u) & trainData(:,5) == -1)),:);
            tEntropy = entropy(tposExample,tnegExample);
            fEntropy = entropy(fposExample,fnegExample);
            thisLevelEntropy = (size(tposExample,1)+size(tnegExample,1))*tEntropy + (size(fposExample,1)+size(fnegExample,1))*fEntropy;
            if thisLevelEntropy < levelEntropy
                levelEntropy = thisLevelEntropy;

                  bestFeature1 = strcat('f',num2str(i),'=',num2str(u)+'^');

                  bestFeature2 = strcat('!f',num2str(i),'=',num2str(u)+'^');

              end
          end
      end
      list1(length(list)+1) = bestFeature1;
      list2(length(list)+1) = bestFeature2;
      dctree(vertcat(tposExample,tnegExample),list1,dominant);
      dctree(vertcat(fposExample,fnegExample),list2,dominant);
  end

%dominant label function
function dm = dominantLabel(trainingData)
    posIndices = find(trainingData(:,5)==1);
    negIndices = find(trainingData(:,5)==-1);
    posCount = size(posIndices,1);
    negCount = size(negIndices,1);
    if posCount > negCount
        dm = 1;
    else
        dm = -1;
    end
end

%entropy function
function en = entropy(tExamples,fExamples)
    posCount = size(tExamples,1);
    negCount = size(fExamples,1);
    pPos = posCount/(posCount+negCount);
    pNeg = 1 - pPos;
    en = -1*(pPos*log(pPos) + pNeg*log(pNeg));
end

[Image Analyst]

How many files do you have? One script and 3 function files? Did you set a breakpoint in your function and check the workspace for the variables? Because, as you know, once the function is done and has exited, it's internal variables will not be seen by the calling routine.

[Kunal Roy]

It's just one file. I called it dtree.m So, if a functions internal variables aren't seen, it means they are there but I can't see them? So if I don't see any output to this program, it's not because the variables inside the functions do nothing? Also, I read somewhere that there can only be one function in program. So, if I put the functions in different files, how would I combine their functions in a single file?

[Stephen23]

"I read somewhere that there can only be one function in program"

Instead of reading random advice on the internet of unknown accuracy, why not just read the MATLAB documentation, which tells everyone exactly how MATLAB works:

https://www.mathworks.com/help/matlab/ref/function.html

https://www.mathworks.com/help/matlab/matlab_prog/create-functions-in-files.html

https://www.mathworks.com/help/matlab/matlab_prog/scripts-and-functions.html

As the documentation clearly states: "Files can include multiple local functions or nested functions"

[Mudambi Srivatsa]

I understand that you are trying to execute MATLAB code and the variables in the decision tree function and others below that do not show up in the workspace. I see that you have one MATLAB file "dtree.m" and all the functions reside in it. Prior to MATLAB R2016b, you cannot have functions in your script file. Executing the script would result in the error with the message "Function definitions are not permitted in this context.". However, starting MATLAB R2016b, you can have functions in your script file. If you are using previous releases of MATLAB, you should create separate files for the functions.

I was able to execute the code "dtree.m" in MATLAB R2016b and all the global variables in the script are loaded. I notice that there are no calls to "dctree" function in your script. Did you happen to remove the function calls when you posted the code here, or you do not have them at all? However, note that even with the proper function calls, the local variables will not be seen in the workspace after the function finishes execution.