about convert time data and plotting

Hi. I have a question about converting time data

I have time data in double and Thickness data of water mass I calculated.

Attached TDD(TDD(:,1)=Thick, TDD(:,2)=time data )

So I draw plot using them.

I want to convert xlabelstick to months.ex) 01 02 03 04 --- 11 12

Thank you for your help.

Answer 1

[Chunru]

load("TDD.mat")
%TDD

subplot(121);
plot(datetime(TDD(:,2),'ConvertFrom','datenum'), TDD(:,1), '.');
datetick('x', "mm/dd");      % doc datetick for more options

subplot(122);
plot(datetime(TDD(:,2),'ConvertFrom','datenum', 'Format', 'MM/dd'), TDD(:,1), '.');

%datetick('x', "MM/dd");      % doc datetick for more options

[주희 박]

Thanks, but i got an error .

Did you multiply 1.0e+05 *?

[Walter Roberson]

You should not use datetick() together with datetime() objects. Instead you should use 'Format' when you construct the datetime() object.

[Chunru]

@Walter Roberson Updated. See the difference.

[Chunru]

@주희 박 No multiplication by 1.0e+05.

[Walter Roberson]

The odd 04/01 has to do with the automatic range selection rounding to "nice" numbers, together with the fact that you asked for month and day number (not for month and year). So the 01/01 is month january (1) day 1 of 2000, and the 04/1 is month april (4) day 1 of 2000.

[Chunru]

I would like to point out that with "datetick('x', "mm/dd")" we can explicitly choose the data format as month/day. With datetime(TDD(:,2),'ConvertFrom','datenum', 'Format', 'MM/dd'), the format is changed to "Jan" and so on. It seems that datetick('x', "mm/dd") should be the command to change the tick setting. The datetime format command seems failed to do so.

[주희 박]

you both so genious. And I can get right answer when I use Matlab2022. (I used 2021 yesterday). Thank you so much. Thanks.

Answer 2

[Walter Roberson]

load TDD
thick = TDD(:,1);
dt = datetime(TDD(:,2),'ConvertFrom', 'datenum', 'Format', 'MM');
scatter(dt, thick, '.')

[주희 박]

Thank you . It is so helpful to me.