How do i retrieve data from a vector of idexes?

Reachnext is a vector that contains the indexes of certain files i want. These files are within the larger file MCR_full.MIB037.Reaches. How do i retrieve the actual files within reachnext and not just their index?

I tried writing the following

temp = (MCR_full.MIB037.Reaches.(reachnext(i,k).kin));

but got this error

Index in position 1 exceeds array bounds. Index must not exceed 1.

any help would be great!

thank you!

[James Tursa]

You need to give us more information. What exactly are the data types and sizes of all of the variables, including the fields, that you are working with?

Answer 1

[Walter Roberson]

Reachnext is a vector that contains the indexes of certain files i want

Then Reachnext contains numeric values? But your code uses reachnext(i,k).kin which would require that reachnext(i,k) evaluates to either a struct or an object

Your code would be consistent with the possibility that reachnext is a struct array and that reachnext(i,j) is a scalar struct that has a field named kin that contains a character vector, and that the contents of that character vector identify a field to use within the scalar struct MCR_full.MIB037.Reaches .

If that were the case then the error would just be that the nonscalar struct reachnext only has one row

[Mackenzie Maher]

I believe you're right but i dont know how to fix it.

Here's the rest of the code.

fn = fieldnames(MCR_full.MIB037.Reaches);       %get fieldnames
allPeaks = cell(10,1);
prominencePeaks = zeros([],[]);
for k = 1:10                                    %loop through first ten reaches
    kins = MCR_full.MIB037.Reaches.(fn{k}).kin; %get kinematics array
    t = kins(:, 1);                             %first column is time
    y = kins(:, 3);                             %third column is 'up'. switch to '2' for 'out'.
    
    %Use findpeaks to get all peak values ('peaks') and locations
    %('peaks_inx'). Only get peaks above prominence 0.1.
    peaks =  findpeaks(y);
    reachLimitArray = find(peaks >= 0.1);
    allPeaks{k} = reachLimitArray; 
    %Plotting
    if length(reachLimitArray) > 1
        disp ('There is at least two value above the limit.')
        f=figure(k);
        hold on;
        
        plot(t, y, 'b-', 'LineWidth', 2);
        plot(t(peaks), peaks, 'rv', 'LineWidth', 2, 'MarkerSize', 12);
        grid on;
        caption = sprintf('Peaks for %s', (fn{k}));
        title(caption, 'FontSize', 18);
        for i = 1:length(reachlimit)
            index = reachLimit(i);
            prominencePeaks(k,i) =  peaks(index);
        end
        
    end
end
peakID = any(prominencePeaks,2);
doublereaches=find(peakID);
reachnext=find(peakID)+1;

[Walter Roberson]

    t = kins(:, 1);                             %first column is time
    y = kins(:, 3);                             %third column is 'up'. switch to '2' for 'out'.
    

Is kins a string() array that contains "up" or "2" or "out" in the third column, and a string-represented time in the first column? I am concerned because in context, your y would have to be a cell array of character vectors, or a categorical array, or a string array, in order to be able to hold the 'up' representation. Of those, categorical is the only one that you might hope to be able to findpeaks() on.

    for i = 1:length(reachlimit)
        index = reachLimit(i);
        prominencePeaks(k,i) =  peaks(index);
    end

You could vectorize part of that:

    high_peaks = peaks(reachlimit);
    prominencePeaks(k,1:length(high_peaks)) = high_peaks;