How to append values to an array in for loop?

Question

Atanu 2022-5-5

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1712245-how-to-append-values-to-an-array-in-for-loop

评论： Atanu 2022-5-8

direction_change.mat

rotation_time_by_direction = [];
for i = 1:10:length(direction_table.rodent_RecordingTime)-10
    direction_change = ones(1,10)';
    for j = 1:10
        direction_change(j,1) = abs(direction_table.direction(i,1)-direction_table.direction(i+j,1));
        threshold_degree = 100;
        if any(direction_change > threshold_degree)
            rotation_time_by_direction = cat(1, rotation_time_by_direction, direction_table.rodent_RecordingTime(i));
        end 
    end
end

I am trying append the rodent_RecordingTime values to rotation_time_by_direction array when rotation is more than 100 degrees over next 10 time steps. But I am not sure why the rodent_RecordingTime is appending to the array. I have attached the variables if you want to look at it. Any help is appreciated.

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Stephen23 2022-5-5

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"But I am not sure why the rodent_RecordingTime is appending to the array."

cat(1, rotation_time_by_direction, direction_table.rodent_RecordingTime(i))
%                                                  ^^^^^^^^^^^^^^^^^^^^

Atanu 2022-5-5

Sorry, I didn't get your comment. If you are asking what do I mean by "But I am not sure why the rodent_RecordingTime is appending to the array.", you can consider it redundant.

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Answer 1

dpb 2022-5-5

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1712245-how-to-append-values-to-an-array-in-for-loop#answer_957715

在 MATLAB Online 中打开

>> for i=1:10:height(direction_table)-10
dx=abs(direction_table.direction(i+1:i+9)-direction_table.direction(i));
ix=find(dx>100,1);
id=ix+i-1;
if any(ix), disp([direction_table{i,:} dx(ix)]),end
end
            0      -5.1105      -465.77      -72.713       107.33
            4       146.82      -398.22      -228.38       324.64
           12      -126.12      -125.06      -378.62        102.2
           13      -111.11      -120.79      -379.49       289.69
           14       168.73       -118.5      -374.87       215.66
           17       177.23      -118.23      -382.94       352.16
>> 

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Walter Roberson 2022-5-7

在 MATLAB Online 中打开

x(end+1,:) = etc

Atanu 2022-5-8

在 MATLAB Online 中打开

Thank you everyone for your comments. I kept on trying with append method, and I think this gives me the result I wanted.

load('direction_table.mat');
rotation_time_by_direction = [];
for i = 1:10:height(direction_table)-10
    direction_change = ones(1,10)';
    for j = 1:10
        direction_change(j,1) = abs(direction_table.direction(i,1)-direction_table.direction(i+j,1));
    end
    threshold_degree = 100;
    if any(direction_change > threshold_degree)
        rotation_time_by_direction = [rotation_time_by_direction; direction_table.rodent_RecordingTime(i)];
    end
end
n_direction_table = direction_table{ismember(direction_table.rodent_RecordingTime,rotation_time_by_direction), :};