plot a line graph with HH:MM:SS in X-axis

I have imported excel data to matlab and i need to plot a line graph where my x axis is date and time in HH:MM:SS and Y axis is power in kW. My X-axis data is as follows.

How can I plot a line graph using this as my x axis? Becacuse when I plot using this, my graph becomes messy. But when I use my x-axis data as 1,2,3,4,5 etc instead of time and data values the graph becomes perfect.

Answer 1

[Walter Roberson]

Use readtable to read in ss a datetime variable and a duration variable, and add the two together to get your x values. set the Format property of the result to appropriate, probably 'HH:mm:ss'. plot can use datetime objects as the x values without difficulty.

[Eranja Noopehewa]

please be kind enough to give me the specific functions and if possible the step by step procedure?

[Walter Roberson]

T = readtable(filename) ;
X = T{:, 1} + T{:, 2};
X.Format = 'HH:mm:ss' ;
Y = T{:, 3};
plot(X, Y)

[Eranja Noopehewa]

thank you..

Here there is a small problem with readtable. This gives me an error when i try to import

Eg: T =readtable('ee.xlsx'); % (ee is my .xlsx file )

Error using readtable (line 198)

An internal error occurred.

Error in cc (line 1)

T = readtable('ee.xlsx');

[Walter Roberson]

Please attach your file for testing. Also, which version are you using and which operating system?

[Eranja Noopehewa]

I have attached the excel file.

My Matlab version is R2017a

OS- Windows 10

[Walter Roberson]

filename = 'ee.xlsx';
T = readtable(filename) ;   %ignore the warning about modified column names
X = T{:,6} + days(T{:,4});
P1 = T{:,1};
P2 = T{:,2};
P3 = T{:,3};
plot(X, [P1, P2, P3]);
legend({'Power 1', 'Power 2', 'Power 3'});

I tested this on R2017a on Mac.

I suspect that you have problems with your Excel. In your release, readtable() on MS Windows will always try to form a connection to Excel to do the reading, and if Excel cannot be reached it will fall back to portable code that does not need Excel. You could end up with an internal error message like you saw if the attempt to reach Excel resulted in a problem.

For debugging purposes, would it be practical for you to uninstall Excel for now? That would enable readtable() to use its internal code to do the reading.

New enough versions of MATLAB now default to using the internal code unless you specifically tell it to use Excel; I think R2019b was the first release for that feature.

[Eranja Noopehewa]

Thank You for the support given.