Plot distance with time

Hi team,

I have an excel file with data in the following format.

 serial time  ID   x
28203        1   341.557
28203        2   374.237
28203.2        1   339.891
28203.2        2   372.506
28203.3        1   338.224
28203.3        2   370.709
28203.5        1   336.558
28203.5 .     2   368.849

serial time is from 12am.I have many vehicle ID s and im trying to plot the graph of x against time for various time's.

Tab=readtable('Trial1.xlsx');
T=Tab{:,2:4};
x=max(T(:,2));
for n=1:x
  A=T(T(:,2)==n,:);
  plot(A(:,1),A(:,3),'DisplayName',num2str(n));
  hold on;
end
hold off
grid on
end

My questions are,

1.is there a better way to do this?

2.how to convert serial time to actual time for the x axis ('HH:MM:SS' format)?

Thanks

[Walter Roberson]

Is it possible that your actual times are, for example, 16-Mar-1977 04:48:00 ?

Which MATLAB release are you using?

[Matlab Newbee]

I am using 2017b. Yes it is correct, i need times such as 7:20:25 am

[SRT HellKitty]

Walter Roberson is basically asking if the serial time is already in MATLAB's serial date format which is (date.time), so evaluating your first datapoint in MATLAB give the date of March 1977. Whereas your data is (I believe...) simply time data without the date. What you can do is use the function datestr() to convert your data to time, but since you have time data you will need to add 6 digits for the date. Something like this 737068 is today's date(you can try datenum(now)). so if you try

datestr(737068.28203)

for your first data sample it should be correct(will give you 06:46)

[Walter Roberson]

No, I suspect that the number is excel serial date format. Converting from that format gives dates in 1977.

Answer 1

[Walter Roberson]

Take the second column of your data and use it as input to datetime with the option 'convertfrom', 'Excel'. You can use the result as the x axis directly in R2016b or later. You can use the Format option of the datetime call to control how the dates appear on the axes.

[Matlab Newbee]

Thank you, yes it worked. Could you please explain how I can use the result as the x axis directly?

AS the converted array os of char, and the other values are double, wouldnt that matter?

[Walter Roberson]

Example:

Tab = readtable('Trial1.xlsx');
excel_timestamp = Tab{:,2};
timestamp = datetime(excel_timestamp, 'ConvertFrom', 'excel');
data_to_plot = Tab{:,4};
plot(timestamp, data_to_plot);

[engesraa]

walter Roberson do you have an idea how i plot a grid for path planning ,please help me

[Walter Roberson]

That is an unrelated matter that should be in its own Question.

Look at the grid command.

Answer 2

[Peter Perkins]

I'm gonna make a different guess: those numbers are seconds since midnight. So:

>> t = readtable('Trial1.xls');
Warning: Variable names were modified to make them valid MATLAB identifiers. The original names are saved in the
VariableDescriptions property. 
>> head(t)
ans =
  8×12 table
    identifier    TimeStamp_sinceMidnight_    idVeh    xCurrentPos    yCurrentPos    zCurrentPos    CurrentSpeed    PreviousSpeed    idSection_idJunction    xCurrentPosBack    yCurrentPosBack    zCurrentPosBack
    __________    ________________________    _____    ___________    ___________    ___________    ____________    _____________    ____________________    _______________    _______________    _______________
        1                  28200                1        373.22         22.983            0              40              40                  449                 385.22             22.822                0       
        2                  28200                1        371.56         23.005            0              40              40                  449                 383.55             22.844                0       
        3                  28200                1        369.89         23.027            0              40              40                  449                 381.89             22.866                0       
        4                  28201                1        368.22          23.05            0              40              40                  449                 380.22             22.889                0       
        5                  28201                1        366.56         23.072            0              40              40                  449                 378.55             22.911                0       
        6                  28201                1        364.89         23.095            0              40              40                  449                 376.89             22.933                0       
        7                  28201                1        363.22         23.117            0              40              40                  449                 375.22             22.956                0       
        8                  28201                1        361.56         23.139            0              40              40                  449                 373.56             22.978                0       
>> t.TimeStamp_sinceMidnight_ = duration(0,0,t.TimeStamp_sinceMidnight_);
>> head(t)
ans =
  8×12 table
    identifier    TimeStamp_sinceMidnight_    idVeh    xCurrentPos    yCurrentPos    zCurrentPos    CurrentSpeed    PreviousSpeed    idSection_idJunction    xCurrentPosBack    yCurrentPosBack    zCurrentPosBack
    __________    ________________________    _____    ___________    ___________    ___________    ____________    _____________    ____________________    _______________    _______________    _______________
        1                 07:50:00              1        373.22         22.983            0              40              40                  449                 385.22             22.822                0       
        2                 07:50:00              1        371.56         23.005            0              40              40                  449                 383.55             22.844                0       
        3                 07:50:00              1        369.89         23.027            0              40              40                  449                 381.89             22.866                0       
        4                 07:50:00              1        368.22          23.05            0              40              40                  449                 380.22             22.889                0       
        5                 07:50:00              1        366.56         23.072            0              40              40                  449                 378.55             22.911                0       
        6                 07:50:00              1        364.89         23.095            0              40              40                  449                 376.89             22.933                0       
        7                 07:50:01              1        363.22         23.117            0              40              40                  449                 375.22             22.956                0       
        8                 07:50:01              1        361.56         23.139            0              40              40                  449                 373.56             22.978                0       
>> tt = table2timetable(t,'RowTimes','TimeStamp_sinceMidnight_');
>> head(tt)
ans =
  8×11 timetable
    TimeStamp_sinceMidnight_    identifier    idVeh    xCurrentPos    yCurrentPos    zCurrentPos    CurrentSpeed    PreviousSpeed    idSection_idJunction    xCurrentPosBack    yCurrentPosBack    zCurrentPosBack
    ________________________    __________    _____    ___________    ___________    ___________    ____________    _____________    ____________________    _______________    _______________    _______________
    07:50:00                        1           1        373.22         22.983            0              40              40                  449                 385.22             22.822                0       
    07:50:00                        2           1        371.56         23.005            0              40              40                  449                 383.55             22.844                0       
    07:50:00                        3           1        369.89         23.027            0              40              40                  449                 381.89             22.866                0       
    07:50:00                        4           1        368.22          23.05            0              40              40                  449                 380.22             22.889                0       
    07:50:00                        5           1        366.56         23.072            0              40              40                  449                 378.55             22.911                0       
    07:50:00                        6           1        364.89         23.095            0              40              40                  449                 376.89             22.933                0       
    07:50:01                        7           1        363.22         23.117            0              40              40                  449                 375.22             22.956                0       
    07:50:01                        8           1        361.56         23.139            0              40              40                  449                 373.56             22.978                0

I'm guessing you then want to do something like

j = (tt.idVeh == i)
plot(tt.Time(i),tt.xCurrentPos(i))

in a loop for i = 1:max(tt.idVeh).