Time Series analysis problems with date

Question

mike 2021-1-4

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回答： Biral Pradhan 2022-1-25

Hi all-and a happy new year (lets hope its better than the last one......)

My query concerns time series.

I have a dataset which consists of 7 seperate excel files, first column is date and second column is a scalar number.

The date is a period of 8 months, jan-aug for 10 years (repeated in each excel file).

I have plotted the first file and the first 8 months plot fine for the ten year period, however, the sep-dec period is also plotted which shows no data, therefore there is a straight line until the next year starts on the graph.

I have used the code

= datevec(cam{:,1}); and also tried

= datenum (cam{:,1});

both do not work!!

So my question is how do I plot the data for just the dates shown which Jan 1st-Aug 31st 2010-2020?

Im fairly new to all this, I have tried using the mathworks help section and tried several other pieces of code, but I get the dreaded red writing, I apologise if this is a billy basic question!

many thanks in advance

Mike

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Adam Danz 2021-1-17

Is the goal to remove the straight line from the data while maintaining the sept-dec dates along the x axis? Or is the goal to remove the gap completly and jump from Aug to Jan along the x axis?

mike 2021-1-17

Hi Adam,

Ideally to remove the lines and the gaps from the x axis so that I can them smooth and detrend.

Cheers

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Answer 1

Biral Pradhan 2022-1-25

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https://ww2.mathworks.cn/matlabcentral/answers/708593-time-series-analysis-problems-with-date#answer_881445

I understand, you want to remove the straight line as well as x-axis labels corresponding to those 4 months (Sep-Dec) for each year. I assume, you plan on interpolating the data for these 4 months later. While plotting monthly data using datetime values from different tables (as in your case), the axis spacing is determined uniformly, so you get labels separated by 1 calendar month.

I do not think it is possible to abruptly change the spacing from 1 calender month to 4 abruptly. A workaround would be to use a timetable and resample your data.