MATLAB: Import large csv file

csvdata import

hello, I have a 22 digit count in the first column of my csv file and all the numbers are important. But Matlab has written the number as E21 and losing significant figures, what should I do? and I have more than one question I just want to get the 1st, 3rd and 5th columns, how can I do?

Best Answer

You cannot read in the first field as numeric. There is no support in the built in types for 22 decimal digits of precision.

detectImportOptions on the file and set the variable type for the first field to be string and readtable with that options structure.

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MATLAB: Reading .txt file

Well, yes you can't read that as a single number. You can either store the whole lot as a vector of digit characters:

digits_text = fileread('digits.txt');

Or convert that to a vector of numbers in the range 0-9:

digits_numeric = digits_text - '0';

Be aware that digits_numeric will use 4 times as much memory as digits_text to store exactly the same information.

You can also store the digits as 8-bit integers (for half the memory of digits_text) but that may hampers you depending on what you want to do with these digits afterwards.

digits_uint8 = uint8(digits_text) - '0';

MATLAB: Is there loss of precision when writing values using CSVWRITE in MATLAB 7.0 (R14)

The CSVWRITE function converts numbers to short format before writing them to the file. To preserve precision, use the DLMWRITE function to explicitly set the precision of the data in the CSV-file:

dlmwrite('filename.csv', [1.23456789], 'delimiter', ',', 'precision', 9);

Best Answer

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MATLAB: Reading .txt file

MATLAB: Is there loss of precision when writing values using CSVWRITE in MATLAB 7.0 (R14)

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