How do I plot a timeseries?

I have data in an excel table. The first comlumn has time data (HH:MM.S) and the other 2 columns have wave height data. I need to plot the data with heights on the y-axis and the time on the x-axis. How do I go about this? I am mainly having trouble getting MATLAB to properly read the time data.

Answer 1

[Star Strider]

Use readtable. You can either use detectImportOptions to import the time as a datetime variable, or convert it after importing the file.

Answer 2

[Hassaan]

SInce I dont have your exact data file. Here is the initial approach you can try:

% Step 1: Import the Data
filename = 'your_file_name.xlsx'; % Replace 'your_file_name.xlsx' with your actual file name
data = readtable(filename);

% Step 2: Convert Time Data
% Assuming the time data is in the first column
% This part may need to be adjusted based on your specific time format
timeStrings = data.Var1; % Adjust 'Var1' if your variable name is different

% Preprocess and convert time strings to durations
% This assumes your time is in an unusual format and needs to be converted
% Example conversion (you may need to adjust this to fit your actual data format)
timeFormatted = strrep(timeStrings, '.', ':'); % Replace '.' with ':' to fit HH:MM:SS format
timeDurations = duration(timeFormatted, 'InputFormat', 'hh:mm:ss');

% Step 3: Plot the Data
% Assuming your wave height data is in the second and third columns
waveHeight1 = data.Var2; % Adjust 'Var2' if your variable name is different
waveHeight2 = data.Var3; % Adjust 'Var3' if your variable name is different

figure; % Create a new figure window
plot(timeDurations, waveHeight1, 'LineWidth', 1.5); % Plot first wave height dataset
hold on; % Hold on to plot the second dataset on the same figure
plot(timeDurations, waveHeight2, 'LineWidth', 1.5); % Plot second wave height dataset
hold off; % Release the plot

% Enhancing the plot with labels and legend
xlabel('Time');
ylabel('Wave Height (units)'); % Replace 'units' with your actual units of measurement
legend('Wave Height 1', 'Wave Height 2'); % Adjust the legend labels as necessary
title('Wave Height Over Time');

% Optionally, you can format the x-axis to display the time more clearly
ax = gca; % Get current axes
ax.XTickLabelRotation = 45; % Rotate the x-axis labels for better readability

Important Notes:

• If your time data doesn't precisely fit the HH:MM.S format or MATLAB has trouble interpreting it, you might need to preprocess your time data in Excel or MATLAB to ensure it's in a recognizable time format.
• The duration function and the InputFormat used in the conversion depend heavily on the exact format of your time data. If the format differs significantly from HH:MM.S, you'll need to adjust the InputFormat accordingly.

This should give you a good starting point. If your data or its format varies significantly from what's assumed here, you may need to tweak the steps accordingly.

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Answer 3

[Adam Danz]

Use readtimetable to create a timetable from your data file. If you're having problems with this step, provide a sample of your data including the headers.

After loading the timetable TT, plot the table variables using plot(TT,{'Var1','Var2'}) where Var1 and Var2 are your timetable variable names The x-values will be the timetable time stamps.

Here's a demo:

% Create timetable
MeasurementTime = datetime(2015,1,1)+days(0:5:600)';
Temp = 20+10*sin(linspace(0,10*pi,numel(MeasurementTime)))';
Pressure = randn(numel(MeasurementTime),1)*5+30;
WindSpeed =  randn(numel(MeasurementTime),1)*10+10;
TT = timetable(MeasurementTime,Temp,Pressure,WindSpeed)

TT = 121×3 timetable
    MeasurementTime     Temp     Pressure    WindSpeed
    _______________    ______    ________    _________

    01-Jan-2015            20     28.426       7.3588 
    06-Jan-2015        22.588     23.303       5.9491 
    11-Jan-2015            25     36.502        27.73 
    16-Jan-2015        27.071     30.975       15.728 
    21-Jan-2015         28.66     26.652       -1.005 
    26-Jan-2015        29.659     31.224     -0.46994 
    31-Jan-2015            30     35.825       2.1641 
    05-Feb-2015        29.659     27.339       25.123 
    10-Feb-2015         28.66      27.85       17.184 
    15-Feb-2015        27.071     23.433      -2.2436 
    20-Feb-2015            25     30.963        27.34 
    25-Feb-2015        22.588     29.617       20.146 
    02-Mar-2015            20     30.544      -2.4134 
    07-Mar-2015        17.412     27.977       29.857 
    12-Mar-2015            15     38.619        21.15 
    17-Mar-2015        12.929     27.226       16.918 

% Plot timetable, specify which table variables to plot
plot(TT,{'Temp','Pressure','WindSpeed'})
legend()