Changing numbers to actual dates

Question

john doe 2018-4-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/394111-changing-numbers-to-actual-dates

评论： dpb 2018-4-11

采纳的回答： dpb

So I have a set of data for example

A = [4 6 3 6 2 7 3 7 8 10]

with time steps

T = [0 28 56 91 119 147 161 175 203 231]

Where the timesteps correspond to months, so 0 is 7th july, 28 is 4th August and so on.

I can plot these graphs, but I would like the numbers to correspond to the actual dates. How can I do this?

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Answer 1

dpb 2018-4-11

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https://ww2.mathworks.cn/matlabcentral/answers/394111-changing-numbers-to-actual-dates#answer_314563

在 MATLAB Online 中打开

>> DT=datetime(2018,7+T.',7)
DT = 
  10×1 datetime array
   07-Jul-2018
   07-Nov-2020
   07-Mar-2023
   07-Feb-2026
   07-Jun-2028
   07-Oct-2030
   07-Dec-2031
   07-Feb-2033
   07-Jun-2035
   07-Oct-2037
>>

Oooops! T (as I kinda' thought) isn't in months; it's days...so

>> DT=datetime(2018,7,7+T.')
DT = 
  10×1 datetime array
   07-Jul-2018
   04-Aug-2018
   01-Sep-2018
   06-Oct-2018
   03-Nov-2018
   01-Dec-2018
   15-Dec-2018
   29-Dec-2018
   26-Jan-2019
   23-Feb-2019
>>

Ah! That looks more realistic!

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john doe 2018-4-11

在 MATLAB Online 中打开

I don't suppose you know how to get it working for error bars do you? When I try to plot error bars, I get given the error;

    Warning: Error updating ErrorBar.
     Undefined function 'double' for input arguments of type
     'datetime'. To convert from datetimes to numeric, first
     subtract off a datetime origin, then convert to numeric using
     the SECONDS, MINUTES, HOURS, DAYS, or YEARS functions.

I am trying to use

errorbar(DT, A, SE)

Where

SE = [0.42 0.76 0.45 0.56 0.345 0.45 0.676 0.456 0.35 0.245]

dpb 2018-4-11

timedate is quite "ripe" yet; there are still holes that need filling. I suggest throw an enhancement request over the wall via official support link just to get it on record somebody wanted the feature with time axes.

The workaround is to revert to the venerable datenum; it is just a double of a specific magnitude. Then, of course, you have to revert to datetick to get the axis displayed as calendar times; somewhat klunky but it does work.

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