# How to extract time (HH:mm) from datetime from a table and plot it in interval range?

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Dennis Huver 2017년 8월 29일
댓글: Dennis Huver 2017년 8월 30일
I have a table with datetime columns and cells and numbers too. The datetime are in default format. I want to extract only the hours from the datetime, and plot it with the column of class double. So, y axis to have the "double" column and x "datetime" but x axis to have intervals such as 00:00-02:00, 02:00-04:00,.....14:00-16:00...22:00-00:00. There are a lot of dates,and what I am trying to do is analyse them in HH:mm rather than chronologically by year and full datetime format. Thanks

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### 채택된 답변

Guillaume 2017년 8월 29일
편집: Guillaume 2017년 8월 29일
Note that the format of the datetime array is irrelevant. It is only used for display. You could of course change the Format so that it only shows hours and minutes but calculations would still involve the date as well.
You use the hour and minute functions to extract the hours and minutes from a datetime array. Alternatively, you use the Hour and Minute properties of the datetime object.
d = datetime + hours(1:10)' + minutes(1:10)'; %create demo datetime a array
hour(d) %get the hour
d.Hour %another way
minute(d) %get the minute
d.Minute %another way
As for the plot, I'm unclear what you want to do. If two values have the same hours and minutes but different day, do you want to plot them at the same abscissa, like a scatter plot?
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Guillaume 2017년 8월 30일
Still not very clear what it is exactly you are doing but glad you solved it. It does sound like you want to clump your data by two hours interval. If that is so, then as Peter said, the discretize function would be the easiest way to do it.
Dennis Huver 2017년 8월 30일
+ found this in the archive which helped a lot. hour_decimal = t.Hour+t.Minute/60; plot(hour_decimal,data) now I have the plot I needed. Thanks a lot btw!

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### 추가 답변 (1개)

Peter Perkins 2017년 8월 29일
I'm not entirely clear what you are trying to do in this plot. It sounds like you want to plot things against time of day, not against absolute time. In recent versions of MATLAB, you can do that just as
plot(timeofday(t.TimeStamp),t.Y)
But then you mention something that sounds like you want to discretize the data into 2hr bins. I'm not sure how that would work in a plot, but the discretize function might be some help.

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