scatterplot with the datetime

Hello everyone,

I am learning Matlab from very basic. I am quite clear what to do but, I am not sure how to procced. I have a dataset with 8 columns. The first one is datetime and other are power consumption. I want to scatter plot the given data according to hours throughout the year with the second column. As the datetime column has hourly based data I am not sure how to extract that data and scatterplot it.

Your help would be highly appericiated.

Answer 1

[Star Strider]

One approach —

Uz = unzip('https://www.mathworks.com/matlabcentral/answers/uploaded_files/630240/household_power_consumption_2007.zip')

Uz = 1×1 cell array
    {'household_power_consumption_2007.csv'}

T1 = readtable(Uz{1})

T1 = 521669×8 table
          DateTime          Global_active_power    Global_reactive_power    Voltage    Global_intensity    Sub_metering_1    Sub_metering_2    Sub_metering_3
    ____________________    ___________________    _____________________    _______    ________________    ______________    ______________    ______________

    01-Jan-2007 00:00:00            2.58                   0.136            241.97           10.6                0                 0                 0       
    01-Jan-2007 00:01:00           2.552                     0.1            241.75           10.4                0                 0                 0       
    01-Jan-2007 00:02:00            2.55                     0.1            241.64           10.4                0                 0                 0       
    01-Jan-2007 00:03:00            2.55                     0.1            241.71           10.4                0                 0                 0       
    01-Jan-2007 00:04:00           2.554                     0.1            241.98           10.4                0                 0                 0       
    01-Jan-2007 00:05:00            2.55                     0.1            241.83           10.4                0                 0                 0       
    01-Jan-2007 00:06:00           2.534                   0.096            241.07           10.4                0                 0                 0       
    01-Jan-2007 00:07:00           2.484                       0            241.29           10.2                0                 0                 0       
    01-Jan-2007 00:08:00           2.468                       0            241.23           10.2                0                 0                 0       
    01-Jan-2007 00:09:00           2.486                       0            242.18           10.2                0                 0                 0       
    01-Jan-2007 00:10:00           2.492                       0            242.46           10.2                0                 0                 0       
    01-Jan-2007 00:11:00             2.5                       0            242.88           10.2                0                 0                 0       
    01-Jan-2007 00:12:00           2.494                       0            242.57           10.2                0                 0                 0       
    01-Jan-2007 00:13:00           2.492                       0            242.41           10.2                0                 0                 0       
    01-Jan-2007 00:14:00            2.48                       0            241.81           10.2                0                 0                 0       
    01-Jan-2007 00:15:00           2.478                       0            241.73           10.2                0                 0                 0       

figure
scatter(T1.DateTime, T1.Global_active_power, '.')
grid

MeanHourlyConsumption  = groupsummary(T1, 'DateTime', 'hourofday', 'mean', 'Global_active_power')

MeanHourlyConsumption = 24×3 table
    hourofday_DateTime    GroupCount    mean_Global_active_power
    __________________    __________    ________________________

            0               21741               0.74066         
            1               21720                0.5522         
            2               21719               0.46917         
            3               21720               0.42062         
            4               21720               0.41507         
            5               21720               0.42935         
            6               21720               0.80487         
            7               21720                1.4331         
            8               21699                 1.502         
            9               21719                1.3085         
            10              21720                1.2181         
            11              21719                1.1809         
            12              21717                1.1473         
            13              21720                1.0948         
            14              21756                1.0827         
            15              21780                1.0167         

figure
scatter(MeanHourlyConsumption{:,1}, MeanHourlyConsumption{:,3}, 's')
grid

.

[Ram Basnet]

Thankyou so much Star strider. I want to ask you another question as well. Can you please help me in finding the total Global active power for every single hour of each day throughout the year.

[Star Strider]

As always, my pleasure!

‘Can you please help me in finding the total Global active power for every single hour of each day throughout the year.’

I believe that is in the first plot.

[Ram Basnet]

the given data is taken for every single minute but for my problem i am trying it to convert it to hour.

Also, The above first plot gives me the total mean for every single hour.

[Star Strider]

My apologies — I missed that detail.

The code needs only a small modification —

Uz = unzip('https://www.mathworks.com/matlabcentral/answers/uploaded_files/630240/household_power_consumption_2007.zip');
T1 = readtable(Uz{1})

T1 = 521669×8 table
          DateTime          Global_active_power    Global_reactive_power    Voltage    Global_intensity    Sub_metering_1    Sub_metering_2    Sub_metering_3
    ____________________    ___________________    _____________________    _______    ________________    ______________    ______________    ______________

    01-Jan-2007 00:00:00            2.58                   0.136            241.97           10.6                0                 0                 0       
    01-Jan-2007 00:01:00           2.552                     0.1            241.75           10.4                0                 0                 0       
    01-Jan-2007 00:02:00            2.55                     0.1            241.64           10.4                0                 0                 0       
    01-Jan-2007 00:03:00            2.55                     0.1            241.71           10.4                0                 0                 0       
    01-Jan-2007 00:04:00           2.554                     0.1            241.98           10.4                0                 0                 0       
    01-Jan-2007 00:05:00            2.55                     0.1            241.83           10.4                0                 0                 0       
    01-Jan-2007 00:06:00           2.534                   0.096            241.07           10.4                0                 0                 0       
    01-Jan-2007 00:07:00           2.484                       0            241.29           10.2                0                 0                 0       
    01-Jan-2007 00:08:00           2.468                       0            241.23           10.2                0                 0                 0       
    01-Jan-2007 00:09:00           2.486                       0            242.18           10.2                0                 0                 0       
    01-Jan-2007 00:10:00           2.492                       0            242.46           10.2                0                 0                 0       
    01-Jan-2007 00:11:00             2.5                       0            242.88           10.2                0                 0                 0       
    01-Jan-2007 00:12:00           2.494                       0            242.57           10.2                0                 0                 0       
    01-Jan-2007 00:13:00           2.492                       0            242.41           10.2                0                 0                 0       
    01-Jan-2007 00:14:00            2.48                       0            241.81           10.2                0                 0                 0       
    01-Jan-2007 00:15:00           2.478                       0            241.73           10.2                0                 0                 0       

% figure
% scatter(T1.DateTime, T1.Global_active_power, '.')
% grid
HourlyConsumption  = groupsummary(T1, 'DateTime', 'hour', 'mean', 'Global_active_power')

HourlyConsumption = 8698×3 table
       hour_DateTime        GroupCount    mean_Global_active_power
    ____________________    __________    ________________________

    01-Jan-2007 00:00:00        60                 2.5506         
    01-Jan-2007 01:00:00        60                 2.5234         
    01-Jan-2007 02:00:00        60                 2.5823         
    01-Jan-2007 03:00:00        60                 2.5417         
    01-Jan-2007 04:00:00        60                 2.4757         
    01-Jan-2007 05:00:00        60                 2.4762         
    01-Jan-2007 06:00:00        60                 2.4558         
    01-Jan-2007 07:00:00        60                 2.4472         
    01-Jan-2007 08:00:00        60                 2.4417         
    01-Jan-2007 09:00:00        60                 3.1461         
    01-Jan-2007 10:00:00        60                 2.6617         
    01-Jan-2007 11:00:00        60                  2.576         
    01-Jan-2007 12:00:00        60                 2.6159         
    01-Jan-2007 13:00:00        60                 2.1624         
    01-Jan-2007 14:00:00        60                 1.2944         
    01-Jan-2007 15:00:00        60                 1.9092         

figure
scatter(HourlyConsumption{:,1}, HourlyConsumption{:,3}, '.')
grid
xlim([HourlyConsumption{1,1} HourlyConsumption{481,1}])             % Temporarily Limit For Readability
Ax = gca;
Ax.XTick = HourlyConsumption{1:24:end,1};
Ax.XTickLabelRotation = 90;
Ax.XMinorTick = 'on';

% pos = Ax.Position;
% Ax.Position = pos+[-500 0 500 0];

Changing the code was straightforward, however making the plot readable was not. (Plotting tick values only for the days works to an extent.) It turns out that ‘hour_DateTime’ is a categorical vector, and it is not obvious that changing its format is an option. It would have to be re-created as a categorical array with a different format, and then substituted for the existing vector to change it. (Changing the datetime Format in ‘T1’ does not change the format in the ‘HourlyConsumption’ table.) Experiment with the 'Position' property to change the width of the plot to improve the readability. (It works in the online Run feature, however it does not do everything I would like it to do here, so I commented it out.)

.

[Ram Basnet]

Thankyou so much. Really appreciate your help.

[Star Strider]

As always, my pleasure!