Subtract I0 from subsequent timetable values

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Poison Idea fan 2021-2-17

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https://ww2.mathworks.cn/matlabcentral/answers/748462-subtract-i0-from-subsequent-timetable-values

评论： Poison Idea fan 2021-2-17

Raw_data_TT_20210217.mat

I have a timetable with different variables corresponding to measurements made with an instrument. One of the variables is a logic variable, "Valve State" that indicates whether the measurement is meant for a background or is a sample measurement.

How could I iterate through the time table and find the most recent variable with "Valve State" == 1 and use that for the calculation on the next chunk of rows which have a "Valve State" == 0?

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Answer 1

Walter Roberson 2021-2-17

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https://ww2.mathworks.cn/matlabcentral/answers/748462-subtract-i0-from-subsequent-timetable-values#answer_626177

在 MATLAB Online 中打开

measurement(valve_state == 0) = nan;
fillmissing(measurement, 'previous')

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Walter Roberson 2021-2-17

在 MATLAB Online 中打开

If you do

VSR = reshape(valve_state, 1, []);  %need a row
mask = VSR == 0;
start0 = strfind([0 mask], [0 1]);
stop0 = strfind([mask 0], [1 0]);

Now start0(K) marks the start of a run of 0's and stop0(K) marks the end of the same run. Under the assumption that the first datapoint is a 1 rather than 0, you would use the datapoint at start0(K)-1 . So perhaps something like

basevalue = measurement;
if start0(1) == 1
    basevalue(1:stop0(1)) = something;  %this is the case where the valve started 0
    start0(1) = []; stop0(1) = [];
end
for K = 1 : length(start0)
    basevalue(start0(K):stop0(K)) = basevalue(start0(K)-1);
end