How do i retrieve data from a vector of idexes?

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Mackenzie Maher
Mackenzie Maher 2022-1-26
评论： Walter Roberson 2022-1-27
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!
  1 个评论
James Tursa
James Tursa 2022-1-26
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?

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回答（1 个）

Walter Roberson
Walter Roberson 2022-1-26
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
  2 个评论
Mackenzie Maher
Mackenzie Maher 2022-1-26
编辑：Walter Roberson 2022-1-27
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
Walter Roberson 2022-1-27
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;

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