Save serial datenum as decimal, not scientific notation

Hello,

I'm reading in a csv file containing timestamps as serial numbers. After some computation, I need to save the array back as a csv file. However, when importing, Matlab converts the decimal datenums into scientific format, i.e. 737389.4167 becomes 7.3739e+05 and they're stored in that format. I know this is the case because when I subsequently import the data in Excel, the format is different between original and edited file. This causes problems when importing the files into

I tried to work around it by converting it in str and cells, but that creates other problems when saving as csv.

Matlab R2018a

[file,path] = uigetfile('*.csv');
fn = fullfile(path,file);
A = csvread(fn);
[filepath,filename,ext] = fileparts(fn);
fnout=fullfile(path,strcat(filename,'_edited',ext));
csvwrite(fnout,A)

Any help is really appreciated as this has created a lot of headaches.

[Star Strider]

Please share the original file and the code you are using to read it and write write the new file. Also, what MATLAB version/release are you using?

[Anke Kügler]

edited above. I cannot share any of the data.

Answer 1

[Anke Kügler]

Ok, dlmwrite instead of csvwrite seemed to fix it. So here's what I'm using instead, now:

[file,path] = uigetfile('*.csv');
fn = fullfile(path,file);
A = csvread(fn);
[filepath,filename,ext] = fileparts(fn);
fnout=fullfile(path,strcat(filename,'_edited',ext));
dlmwrite(fnout,A,'precision',15)

Answer 2

[James Tursa]

First, MATLAB stores all doubles the same way ... as IEEE binary floating point format. What you are seeing as "737389.4167 becomes 7.3739e+05" is simply a display issue. The underlying format for both is still IEEE binary floating point. E.g.,

>> x = 737389.4167
x =
   7.3739e+05
>> format long
>> x
x =
     7.373894166999999e+05
>> format short
>> x
x =
   7.3739e+05

As far as your writing to csv being different from what you read in, you need to show us a sample of the csv file and also the code you are using for reading and writing. Then we can help you.

[Anke Kügler]

I understand that and that's what I kept reading everywhere, yet, the problem persists. I've edited my post to include the code, but I cannot share any data. Let me try to reproduce a sample csv file.

[James Tursa]

See also this related post:

https://www.mathworks.com/matlabcentral/answers/477925-what-is-the-best-way-to-save-to-csv-without-losing-precision-and-with-column-headers