How can I export a matrix as a CSV file?

Hi,

I have a 320x2 matrix with doubles. I want to save it in a CSV file in the following pattern:

234,2 671,5 735,1 264,2 346,7 ... etc.

I googled this problem and found the function "csvwrite". However, when I use that function like this

    csvwrite('test.txt',a)

I get the following:

234,2671,5735,1264,2346,7

What is going on here? How can I solve this issue?

Thanks a lot, Toby

[jgg]

Why do you want to export it like that? It seems really unnatural, and will be annoying to accomplish.

[Ian Mclennan]

This thread really helped me, thank you for posting.

Answer 1

[MathWorks Support Team]

"csvwrite" is not recommended. Use "writematrix" to export matrix data as a CSV file instead.

When writing matrix data to a file, you can specify the file type as part of the file name in the second argument of the function call:

m = [234 2;671 5;735 1;264 2;346 7] 
writematrix(m,'M.csv') 

[Trevon McHansen]

To potentially save others an extra click or two, "writematrix" was introduced in R2019a.

[Larry Gulliver]

Thank you!

[Reem]

After I do that, how can I see the csv file?

[Chris]

Look at your file hierarchy on the left you'll see a file that's been generated with the name you gave it. You can right click and show it in explorer.

Answer 2

[Azzi Abdelmalek]

a=[234,2
671,5
735,1]
csvwrite('file.csv',a)

[Shuva Paul]

Great, thanks for the solution :)

[Mehdi BENSEDDIK]

I appreciate you for the sharing

[Bill Tubbs]

Being a Python user coming to Matlab I was a bit shocked to find that csvwrite truncates the data output.

csvwrite('u.csv', u)

File contents:

1000,957.6,917,878.13,840.9, ...

Then I happened to check the documentation and found this:

csvwrite is not recommended. Use writematrix instead. For more information, see Compatibility Considerations.

writematrix(u)

File contents:

1000,957.603280698574,917.004043204671,878.12608018665,840.896415253715, ...

[Guillaume]

writematrix is fairly new and did not exist when this question was ask.

I was a bit shocked to find that csvwrite truncates the data output.

Any conversion of number to text will truncate the representation of most numbers, in python as well. As documented csvwrite has a precision of 5 digits. For more precision, the alternative at the time was dlmwrite. Interestingly writematrix also doesn't have an option of altering the precision and always use longg (15 digits of precision).

Answer 3

[Jos (10584)]

You and your computer disagree on what to use as a decimal symbol: a . or a ,

I strongly recommend you to use a decimal point. Probably that means you have to change your locale / regional settings in the operating system.

Answer 4

[Sindar]

It sounds like all you need to do is print a column vector instead of a row vector. This can be done easily:

csvwrite('test.txt',a.')

The '.' is important only if you have complex data

Answer 5

[Toby Feld]

For some reason the example I used was re-edited by the forum software to let it appear in one line. I cannot figure out how to disable that formatting (seriously, WTF??). So here is how I want the CSV file to look as a png file. I hope the forum does not change graphic files.