How to convert a Year Month and Date to Day Number?

Question

Trisha Mae Roque 2022-5-13

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此问题的直接链接

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评论： Steven Lord 2022-5-13

Good Day! I'm a newbie in Matlab.

I want to ask about converting a whole column that are in date format into a day numbers. It has 2 columns and 824 lines, no headlines. I actually thought of adding another row consist of numbers 1 to 824 then removing the date column but i don't know how to do it.

Here's the sample data in csv.

2020-01-30,1.0

2020-01-31,0.0

2020-02-01,0.0

2020-02-02,1.0

2020-02-03,0.0

Here's my desired product

1,1.0

2,0.0

3,0.0

4,1.0

5,0.0

or

2020-01-30,1.0,1

2020-01-31,0.0,2

2020-02-01,0.0,3

2020-02-02,1.0,4

2020-02-03,0.0,5

Thank you in advance.

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Rik 2022-5-13

What have you tried so far?

Trisha Mae Roque 2022-5-13

It's just reading the file and I'm sorry for that. I don't even know how to access a column without headlines. I know how to use python but matlab is a different ground for me.

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Answer 1

KSSV 2022-5-13

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https://ww2.mathworks.cn/matlabcentral/answers/1718240-how-to-convert-a-year-month-and-date-to-day-number#answer_963145

Load the data from csv file into MATLAB using readtable

You can convert the dates into date numbers using datenum

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Steven Lord 2022-5-13

在 MATLAB Online 中打开

Rather than using datenum to create serial date numbers I recommend using datetime to create a datetime array. Looking at some sample data:

s = ["2020-01-30"
"2020-01-31";
"2020-02-01";
"2020-02-02";
"2020-02-03"];
theFormat = 'yyyy-MM-dd'; % Use for importing and/or displaying

You can use the default display format, which in this case is different from how the data is stored in the string array s:

dt = datetime(s, 'InputFormat', theFormat)
dt = 5×1 datetime array
   30-Jan-2020
   31-Jan-2020
   01-Feb-2020
   02-Feb-2020
   03-Feb-2020

Or you can specify your own display format, which displays it in the same form as the strings in s:

dt = datetime(s, 'InputFormat', theFormat, ...
                 'Format', theFormat)
dt = 5×1 datetime array
   2020-01-30
   2020-01-31
   2020-02-01
   2020-02-02
   2020-02-03