Preserving decimal places when exporting data

Hello,

I am trying to export a matrix as a text file. One of the columns in the matrix represents time in seconds, but with millisecond resolution, so that that the entries look like 1.001,1.002, ... , 300.271 and so on.

Is there a way to export this data while keeping the number of decimal places (in this case 3) constant? I don't want to have the precision of all columns be some set number, I just want the exported data to have the exact same entries as my file - for some reason this is proving difficult.

Would be very grateful for any solutions you might propose. Thank you!

Answer 1

[Star Strider]

You can create a delimited file with fixed formats for each field easily using fprintf.

I used sprintf here to check the output without actually writing the file. The only change needs to be the function and anything else it requires (such as a fileID number):

Data = [1+[0:10]'*1E-3, rand(11, 3)];
File = sprintf('\t%.3f\t%.5f\t%.2f\t%.9f\n', Data');

You can of course change the delimiter. I used a tab here.

[Image Analyst]

To be clear, the number of numbers to the right of the decimal point is the number between the %. and the f. So %.5f would give 5 decimal places to the right of the decimal point. If it's 3, there would be 3, and so on.

[Star Strider]

Thank you Image Analyst. I definitely should have provided a few more details.

Also, note the transpose (') (specifically Data') in the sprintf call. That is necessary to write a matrix with fprintf and sprintf correctly because of the way those functions use their input arguments. If you used a for loop to print the ‘Data’ matrix line-by-line, that would not be necessary. However, using the loop would be much less efficient than using the transposed matrix for this particular problem.