MATLAB Answers

Converting time data to plot

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Ryan McBurney
Ryan McBurney on 10 Sep 2019
Edited: Adam Danz on 16 Sep 2019
I imported an excel file (xlsread) and the time data turned into decimal form. I wrote the following code get a what I think is called a character array of just times.
um_time = num(:,1);
theDate = char(datetime(num_time,'ConvertFrom','excel')); % or 'excel1904'
theTimes = theDate(:,end-7:end);
The output for theTimes variable looks like this
val =
The problem that I have is that I can't use the variable theTimes in a plot function.
How can I turn theTimes values into a column vector of values that I can use to plot?


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Answers (1)

Adam Danz
Adam Danz on 10 Sep 2019
Edited: Adam Danz on 16 Sep 2019
After you convert to datetime, keep it in datetime format. There's no need to convert it to char.
From r2016b onward, you can use datetime objects in plot().
Here's several of examples
If you're reading the dates in from excel you can read them in as datetime.
m = readmatrix('Dates.xlsx','OutputType','datetime');


Ryan McBurney
Ryan McBurney on 12 Sep 2019
I figured out a different approach.
I used readtable() instead of xlsread. I used this code as well:
data = readtable(filename,'Range','A22:Y432');
data.Time = datetime(datevec(data.Time),'Format','HH:mm:ss.SSS');
The second line in the code solved my problem.
Thanks for the nudge in the right direction.
Adam Danz
Adam Danz on 12 Sep 2019
I just updated my answer to add another approach similar to yours.
If you're going to use readtable(), you could use the DateTimeType name-value input instead of doing the conversion in your comment above.

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