convert date to datenum import from excel

hello

I want to import a simple excel file to matlab and convert the column with dates from text to numeric values. The problem is that the rule convert does not show up as an alternativ. I can only replace things. Would be very glad if someone could help.

Answer 1

[Adam Danz]

I agree that readtable() is the better option but if you decide to stick with the import tool, here's an idea.

In the dropdown menu under your variable name 'dag' where it currently says "Number" in your screenshot, select a date and time option. This will convert your timestamps to datetime format. After importing, you can use datenum() to convert them to double if desired.

Here's a screen shot with a different data set.

[ErikJ]

Ok thanks. But if i use datetime for the date column and then click generate function and write the following in my editor:

mytable=importfile('datums.xlsx','Blad1',2,15)

i get the error message: 'Undefined function 'importfile' for input arguments of type 'char'.'

[Walter Roberson]

When you click to generate, it should have created importfile.m

[Adam Danz]

Yeah, that might be the problem. After you select datetime you'll need to re-generate the importfile() function so the new version accounts for the new format.

Answer 2

[Walter Roberson]

We recommend using readtable() instead. With new enough MATLAB, it can help to use detectImportOptions() with readtable()

Answer 3

[ErikJ]

I solved the problem now. Thanks! Now when I have imported the data I calculate new values based on the old. Now I would very much like to add this new values as a new row (=one new value per column) and save this in the excel file (overwrite) without changing the formatting. How can i do this?

Thanks in advance

Erik

[Adam Danz]

Are you looking for xlswrite() ?

[ErikJ]

Yes but how do i use it to write into an existing file?

[Adam Danz]

doc xlswrite()

Read about the inputs and how to use this function. There's even an example that shows you how to insert data into specific cells of the spreadsheet. I was about to type up a quick demo but Matlab's documentation covers it. The best way to learn is by digging into the documentation. If you get stuck, come back.

It would be wise to make a copy of your data as you poke around with this function in case you accidentally overwrite your data.

[ErikJ]

Ok thanks. I'll read about xlswrite()