Concatenate into a matrix is not saving and is overriding every iteration?

I have 2 subjects where each subject has three conditions. I made an array where each row is 1*3 representing one subject with the three conditions. I now want to add each subjects' array together.

However, my code seems to be overwriting every round, when I want:

%subject 1
percent_change = [1 2 3]
%subject 2
percent_change = [3 4 5]

%what I want as ouput:
percent_change_matrix: 1 2 3
                       3 4 5

Here is what I have tried:

%try 1
subjs = {'subject1' 'subject2'}
time = {'30-50' '50-60' '60-70'}

%% defining tac components for pet plot 
for s = 1:length(subjs)
    subj = subjs{s}
for i = 1:length(time)
        time = time{i}
        percent_change(:,i) = ((task-baseline)/baseline)*100 %task=2 baseline=1
end

percent_change_matrix = []
percent_change_matrix = [percent_change_matrix; percent_change]
end

I have also tried:

%try 2
subjs = {'subject1' 'subject2'}
time = {'30-50' '50-60' '60-70'}

%% defining tac components for pet plot 
for s = 1:length(subjs)
    subj = subjs{s}
for i = 1:length(time)
        time = time{i}
        percent_change(:,i) = ((task-baseline)/baseline)*100
end

try
percent_change_matrix = [percent_change_matrix; percent_change]
catch
percent_change_matrix = [percent_change_matrix]
end
end

my output for try 1 and try2 is:

percent_change_matrix: [3 4 5]

There are no errors with eithor of my codes, but the matrixes are not being built upon eachother. Do you have any suggestions? Thanks so much!

[KSSV]

First point is the given code working?

[nines]

Yes the code works! Try 1 and Try 2 have the output:

percent_change_matrix: [3 4 5]

[Ganesh]

Could you elaborate on the variables task and baseline?

[KSSV]

%try 1
subjs = {'subject1' 'subject2'}
time = {'30-50 '50-60' '60-70'}  % this line throws errors

Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

Error in connector.internal.fevalMatlab

Error in connector.internal.fevalJSON

%% defining tac components for pet plot 
for s = 1:length(subjs)
    subj = subjs{s}
for i = 1:length(time)
        time = time{i}
        percent_change(:,i) = ((task-baseline)/baseline)*100
end

percent_change_matrix = []
percent_change_matrix = [percent_change_matrix; percent_change]
end

[nines]

that was a typo for this site, but not in my actual code

[nines]

task and baseline are each going to be equal to one number for each subject and time combination:

here are examples:

subject 1, time 30-50: task: 2, baseline: 1

subject 1, time 50-60: task: 3, baseline: 2

subject 1, time 60-70: task: 3, baseline: 2

subject 2, time 30-50: task: 2, baseline: 1

subject 2, time 50-60: task: 4, baseline: 3

subject 2, time 60-70: task: 5, baseline: 2

[Ganesh]

The issue is that percent_change_matrix is being redefined to an empty array at every iteration for subject. Move the declaration of this to the beginning, or immediately following 'time' variable.

Another issue that may arise seems to be

time = time{i}

This would redefine your time variable. Consider naming one of the variables differently.

Answer 1

[Matt J]

Ns=numel(subjs); Nt=numel(time);

percent_change=cell(Ns,1);
for s = 1:Ns
   subj = subjs{s};
    for i = Nt:-1:1
            ...
            percent_change{s}(:,i) = ((task-baseline)/baseline)*100 %task=2 baseline=1
    end

end

percent_change_matrix=cell2mat(percent_change);