import data from csv file with same format of stored data in file

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sasan basereh on 17 Mar 2024

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Commented: Star Strider on 17 Mar 2024

hi.

i have csv file with arraay of data stored in it such as date, time & values. values are stored with 5 decimal point format. (such as 10.43546)

i want to import it to matlab with readtable. but when importing done, data is stored in 4 decimal point format. (such as 10.4355)

in which way i can import data of csv file & store specific columns with desired format (such as 5 decimal point format).

with thanks

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Stephen23 on 17 Mar 2024

Edited: Stephen23 on 17 Mar 2024

"but when importing done, data is stored in 4 decimal point format."

I doubt that.

Most likely you are confusing the displaying of data with what data are stored in memory. Two different things.

"import data from csv file with same format of stored data in file"

Numeric data classes do not store any format information, so what you are asking for ... does not make much sense in terms of how computers actually store numeric data. In the unlikely event that you really need the exact format then you would need to store the value as text... which is then basically useless for doing any calculations on.

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Answer 1

Star Strider on 17 Mar 2024

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The data are imported and stored with their original precision. They are just displayed with 4 digits to the right of the decimal.

See the format function for options on changing it to display what is actually being imported.

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Star Strider on 17 Mar 2024

Open in MATLAB Online

All the decimal places (and supplied precision) are there.

Use the format function to change the way they are displayed.

Example —

T1 = array2table(randn(6,4))
T1 = 6×4 table
      Var1        Var2         Var3         Var4  
    ________    ________    __________    ________

     -1.4155     0.67983      -0.69693      1.0145
    -0.83542    -0.23211      0.069036    0.087676
     0.44167     0.98351    -0.0075534     0.52034
     -1.3784    -0.56798       0.56168      0.8716
    -0.67062     0.37363       -1.2762     0.34395
    -0.71573      -1.439       0.37903    -0.11116
format longG
T1
T1 = 6×4 table
           Var1                  Var2                   Var3                   Var4       
    __________________    __________________    ____________________    __________________

       -1.415457879134     0.679825171573361      -0.696930111723829      1.01453641214015
    -0.835421662507246    -0.232113754985102      0.0690355498048767    0.0876760349190557
     0.441668898325135     0.983513150948618    -0.00755340839374248      0.52033818978414
     -1.37841321090534    -0.567979259001381       0.561682578306483     0.871604759761926
    -0.670619800307231     0.373628641504333       -1.27615534723442     0.343952276266442
    -0.715726716211453      -1.4389779661055       0.379028110292516    -0.111164116408287

It is not necesary to change the format of the displayed results. This simply demonstrates that the full precision results are saved, and actually exist in the file (table ‘T1’ in this example, since I do not have your file to work with).

.

Stephen23 on 17 Mar 2024

Edited: Stephen23 on 17 Mar 2024

Open in MATLAB Online

"is this for saving data to variable?"

Lets try it right now:

writematrix(10.43546,'test.txt')
M = readmatrix('test.txt')
M = 10.4355

Now lets display the data using a few different approaches:

fprintf('%.5f',M)
10.43546
format long G
M
M = 
                  10.43546

So far the only problem seems to be that you are confusing how data is displayed with the actual data stored in memory. They are not the same thing:

https://www.mathworks.com/help/matlab/ref/format.html

Star Strider on 17 Mar 2024

@Stephen23 — Thank you!

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import data from csv file with same format of stored data in file

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import data from csv file with same format of stored data in file

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