How do I search for and collect column data based on column name?

I have a data set of motion capture variables that is 101x2209. Is there a way to search through the column headers, looking for specific variable names, then storing that found column data in a new matrix? (I attached the first file{1,1} for testing)

ie. I want to find all the "LKneVel" columns in my data set and collect them in a new matrix.

name = 'AM';

subject = ["1.1_", "1.2_", "2.1_", "2.2_"];

Pos = ["LHS-LHS", "RHS-RHS"];

for n = 1:4

for k = 1:2

file{n,k} = strcat(name, subject(n), Pos(k), '.txt');

stuff = readmatrix(file{1,1}); % just testing on the first file

S = readlines(file{1,1});

Head = strsplit(S(2,:)); % now we have an array of the headers and their respective locations

[sizeRH sizeCH] = size(Head); % code from here down is my attempt to search and collect

Search{1} = 'LKneVel';

Search{2} = 'LKneMom';

Search{3} = 'LKnePow';

[sizeRH sizeCS] = size(Search);

for i = 1:sizeCH

for j = 1:sizeCS

if string(Head{i}) == Search(j)

index(j) = i;

end

end

end

end

end

Answer 1

[Voss]

name = 'AM';
subject = ["1.1_", "1.2_", "2.1_", "2.2_"];
Pos = ["LHS-LHS", "RHS-RHS"];

Search = {'LKneVel' 'LKneMom' 'LKnePow'};

n_sub = numel(subject);
n_pos = numel(Pos);
n_search = numel(Search);

file = cell(n_sub,n_pos);

out = cell(n_sub,n_pos,n_search);

for n = 1:n_sub
    for k = 1:n_pos
        file{n,k} = strcat(name, subject(n), Pos(k), '.xlsx');
        [~,~,data] = xlsread(file{n,k});
        data(:,1) = [];
        data(strcmp(data,'NaN')) = {NaN};
        for j = 1:n_search
            out{n,k,j} = cell2mat(data(6:end,strcmp(data(2,:),Search{j})));
        end
    end
end

[KASSIDY KNUTSON]

Thank you!!!