MATLAB: How to add values to a column based on time column and its own column

timetable

What I'm trying to do is add values to a column based on two conditions. I want to locate the time value based on a value in a different column from the same row. Then I want to continue that value from the different column for the next x minutes that I decide on. I'm not really sure how to be phrasing what I would like so I think it's better if I give what I have now and what I would like to achieve.

My current timetable named E has two columns that look like the 10.44.48 Screen Shot

What I want is to replace the 0 with a 2 in the Interval column for any rows after the current 2 for the next, let's say, 3 minutes following the first 2 value in the Interval column. So I'd end up with the 10.47.08 Screen Shot

I want to be able to add the 2 by just relying on the initial interval value, so that I don't have to search for the time values in my data set for all the different interval values I have. My data set will not necessarily have rows separated by one minute intervals which is why I need to specify the time value as well.

I've been using variables like E.Time to specify my columns.

Please help!

Best Answer

If your screen shot example is really all you want to do, then it's this:

i = find(tt.Interval > 0);
tt.Interval(i:end) = tt.Interval(i);

But I'm guessing there's more to what you are asking, and your screen shots don't even match your description. You may be asking for this:

i = find(tt.Interval > 0);
tr = timerange(tt.Time(i),tt.Time(i)+minutes(3);
tt(tr,:).Interval = tt.Interval(i);

Related Solutions

MATLAB: Create subsets of data within a timetable

As you've discovered creating six individually named timetables is not a good idea. As a rule, as soon as you start numbering variables, you're doing something wrong.

starttimes = 0:4:20;
endtimes = 4:4:24;
tts = arrayfun(@(s, e) TT(timerange(hours(s), hours(e)), :), starttimes, endtimes, 'UniformOutput', false);

will create a cell array with your 6 timetables. It's then trivial to iterate over the element of the cell array:

for tidx = 1:numel(tts)
   tts{idx}
   %do something with tts{tidx}, a single timetable
end

Alternatively, instead of looping over the timetables in the cell array, you could indeed just merge them into one by concatenating them vertically:

filteredtt = vertcat(tts{:})

MATLAB: How to read data from a txt file and plot them with dates on the axes

You can use readmatrix to read in your text file. I've chosen to read the date and time in as character values and then I join the date and time to create a datetime column. When you plot with datetime values your axes will show the dates in date format.

% read in the data 
filename='pluie-iut.txt';
varNames = {'date','time','value'};   % name your variables here
varTypes = {'char','char','double'}; 
delimiter = ';';
dataStartLine = 2;
extraColRule = 'ignore';
opts = delimitedTextImportOptions('VariableNames',varNames,...
                                'VariableTypes',varTypes,...
                                'Delimiter',delimiter,...
                                'DataLines', dataStartLine,...
                                'ExtraColumnsRule',extraColRule); 
T = readtable(filename,opts);

Look at the first few rows of the table

head(T)
ans =
  8×3 table
        date            time        value
    ____________    ____________    _____
    {'20180703'}    {'14:50:00'}       0 
    {'20180704'}    {'12:55:00'}       0 
    {'20180704'}    {'13:00:00'}       0 
    {'20180704'}    {'20:40:00'}       0 
    {'20180704'}    {'20:45:00'}     0.4 
    {'20180704'}    {'20:50:00'}       0 
    {'20180704'}    {'20:55:00'}       0 
    {'20180704'}    {'21:00:00'}     0.2

Compute datetime values.

% add datetime column
T.datetime = datetime(strcat(T.date, {' '},T.time), 'Inputformat', 'yyyyMMdd HH:mm:ss');

View the results (first few rows)

head(T)
ans =
  8×4 table
        date            time        value          datetime      
    ____________    ____________    _____    ____________________
    {'20180703'}    {'14:50:00'}       0     03-Jul-2018 14:50:00
    {'20180704'}    {'12:55:00'}       0     04-Jul-2018 12:55:00
    {'20180704'}    {'13:00:00'}       0     04-Jul-2018 13:00:00
    {'20180704'}    {'20:40:00'}       0     04-Jul-2018 20:40:00
    {'20180704'}    {'20:45:00'}     0.4     04-Jul-2018 20:45:00
    {'20180704'}    {'20:50:00'}       0     04-Jul-2018 20:50:00
    {'20180704'}    {'20:55:00'}       0     04-Jul-2018 20:55:00
    {'20180704'}    {'21:00:00'}     0.2     04-Jul-2018 21:00:00

Plot the data

plot(T.datetime, T.value, 'o')

Best Answer

Related Solutions

MATLAB: Create subsets of data within a timetable

MATLAB: How to read data from a txt file and plot them with dates on the axes

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