Converting time data to plot

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Ryan McBurney
Ryan McBurney 2019-9-10
编辑： Adam Danz 2019-9-16
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 =
19:17:10
19:17:10
19:17:10
19:17:10
....
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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回答（1 个）

Adam Danz
Adam Danz 2019-9-10
编辑：Adam Danz 2019-9-16
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().
datetime(num_time,'ConvertFrom','excel')
Here's several of examples
https://www.mathworks.com/help/matlab/matlab_prog/plot-dates-and-durations.html
[addendum]
If you're reading the dates in from excel you can read them in as datetime.
m = readmatrix('Dates.xlsx','OutputType','datetime');
  2 个评论
Ryan McBurney
Ryan McBurney 2019-9-12
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 2019-9-12
编辑：Adam Danz 2019-9-13
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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