Add leading decimal places to numbers in text file

Question

Timbo 2021-2-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/747182-add-leading-decimal-places-to-numbers-in-text-file

编辑： dpb 2021-2-18

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I have data in a text file and would like to change some numbers while keeping the rest of the line the same.

For instance I have:

Name,proj2;
Edition,59;
Start;
Variable,1;
    DataReg,0.00,0.00;
    Area,520.00;
300,221.7467,424.1668,801.0146;
390,117.4175,507.8583,29.2203;
    Area,530.00;
300,488.6090,963.0885,488.8977;
390,578.5251,546.8057,624.0601;
    Datareg,00.00,30.00;
    Area,520.00;
300,367.4366,913.2868,335.3568;
390,987.9820,796.1839,679.7280;
    Area,530.00;
300,106.7619,715.0371,698.7458;
390,653.7573,903.7206,197.8098;
    DataReg,00.00,160.00;
    Area,520.00;
300,291.9841,167.1684,489.6876;
390,431.6512,106.2163,339.4934;
    Area,530.00;
300,522.6770,5147.8709,3201.4549;
390,7137.8581,9142.7370,7101.0988;
    DataReg,30.00,00.00;
    Area,520.00;
300,2121.7467,4214.1668,8201.0146;
390,1217.4175,5107.8583,219.2203;
    Area,530.00;
300,4188.6090,9163.0885,4288.8977;
390,5178.5251,5146.8057,6224.0601;
    Datareg,30.00,30.00;
    Area,520.00;
300,3167.4366,9113.2868,3135.3568;
390,9287.9820,7296.1839,6279.7280;
    Area,530.00;
300,1106.7619,1715.0371,1698.7458;
390,1653.7573,1903.7206,1197.8098;
    DataReg,30.00,160.00;
    Area,520.00;
300,2921.9841,1672.1684,2489.6876;
390,4321.6512,1206.2163,2339.4934;
    Area,530.00;
300,522.6770,57.8709,3021.4549;
390,7327.8581,9422.7370,7021.0988;
    DataReg,160.00,0.00;
    Area,520.00;
300,316.4366,911.2868,313.3568;
390,92.9820,729.1839,627.7280;
    Area,530.00;
300,110.7619,171.0371,169.7458;
390,165.7573,190.7206,119.8098;
    DataReg,160.00,30.00;
    Area,520.00;
300,292.9841,167.1684,248.6876;
390,432.6512,120.2163,233.4934;
    Area,530.00;
300,52.6770,5.8709,302.4549;
390,732.8581,942.7370,702.0988;
DataReg,160.00,160.00;
    Area,520.00;
300,7292.9841,7167.1684,7248.6876;
390,7432.6512,7120.2163,7233.4934;
    Area,530.00;
300,752.6770,75.8709,7302.4549;
390,7732.8581,7942.7370,7702.0988;

(Sorry it's so long, just wanted to paint a vivid picture)

Now, what I want to do is change the numbers in lines containing "DataReg" into the same numbers except with three leading spaces in front of decimal while still containing the two trailing decimal places. For example, I want to change this:

    DataReg,0.00,0.00;
    Datareg,0.00,30.00;
    DataReg,0.00,160.00;
    DataReg,30.00,0.00;
    Datareg,30.00,30.00;
    DataReg,30.00,160.00;
    DataReg,160.00,0.00;
    DataReg,160.00,30.00;
    DataReg,160.00,160.00;

Into this:

    DataReg,000.00,000.00;
    Datareg,000.00,030.00;
    DataReg,000.00,160.00;
    DataReg,030.00,000.00;
    Datareg,030.00,030.00;
    DataReg,030.00,160.00;
    DataReg,160.00,000.00;
    DataReg,160.00,030.00;
    DataReg,160.00,160.00;

Notice how some values (i.e.,160.00) already have three leading places and hence don't need change. keep in mind this will be for a large .txt file and other DataReg numbers such as 170.00, 180.00, 190.00 will exist, but nothing above 999.00 exists. Lots of comments please!

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Answer 1

dpb 2021-2-16

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/747182-add-leading-decimal-places-to-numbers-in-text-file#answer_625117

编辑：dpb 2021-2-16

在 MATLAB Online 中打开

Air code--caution!!!

c=readcell('YourTextFile.ext');         % bring file in as cellstr() array
isDR=startsWith(c,'DataReg');           % logical addressing array of wanted lines
fmt='DataReg,%07.3f,%07.3f;';           % desired output format
c(isDR)=compose(fmt,str2double(split(extractAfter(c(isDR),'DataReg,'),',')));   % rewrite as wanted
writecell(c,'YourNewTextFile.ext','QuoteStrings',0)  % put in new file (can overwrite original once sure is as wanted)

In short, don't try to fix up based on what is there by counting string lengths or such, just write out in the desired format the values that are there.

ADDENDUM:

Above patched to incorporate fixes outlined in Comments...the doc in R2019b is wrong on default behavior of quoted strings in "writecell'; and the release OP is using is same default behavior; whether the doc matches now or not, I don't know. Worthy of reporting the documentation error if doesn't.

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dpb 2021-2-16

编辑：dpb 2021-2-16

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Again, that's air code (which it is/was because you didn't attach a sample file so didn't have easy way to test) -- "help us help you"

It appears that contrary to the doc writecell uses 'QuoteStrings',1 as default instead of as false.

To add the trailing semicolon, fix up the format string

fmt='DataReg,%07.3f,%07.3f;';

It's not hard to figure this stuff out, read the doc and try some things out at command line...be much faster than waiting on us in future. (Now I will grant that thinking of doing in memory this way is a result of more experience than you undoubtedly have; hence the illustration of the concept. Once see that, however, then debugging the little nits to clean things up is an excellent mechanism for learning...and also illustrates why to not overwrite the original file(s) the first time! :) )

>> fmt='DataReg,%07.3f,%07.3f;';
>> compose(fmt,str2double(split(extractAfter(lower(c(1:3)),'datareg,'),',')))
ans =
  3×1 cell array
    {'DataReg,000.000,000.000;'}
    {'DataReg,000.000,030.000;'}
    {'DataReg,000.000,160.000;'}
>> writecell(ans,'tryit.csv')
>> type tryit.csv
"DataReg,000.000,000.000;"
"DataReg,000.000,030.000;"
"DataReg,000.000,160.000;"
>> writecell(ans,'tryit.csv',"QuoteStrings",0)
>> type tryit.csv
DataReg,000.000,000.000;
DataReg,000.000,030.000;
DataReg,000.000,160.000;
>> 

NB: the lower() in the above is owing to the data cut'n pasted from your original posting is not all capitalized regularly -- hence the match for the split string didn't always work so I patched it to convert to lower case and match on that string instead. I presumed in the answer that was a fignewton of the posting and not real in the file.

dpb 2021-2-17

编辑：dpb 2021-2-18

在 MATLAB Online 中打开

Oh. You're going to have same problem with writecell, too, then, it was also not introduced until R2019a.

There's no other way then but to revert to low-level i/o -- this has been an Achilles' heel problem for as long as have had cell arrays...

fid=fopen('YourFile.ext','w');
for r=1:size(c,1)
  fprintf(fid,'%s\n',c{r});
end
fclose(fid);

Timbo 2021-2-17

The work-arounds worked! Managed to make the changes I needed. Thank you kindly!

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Add leading decimal places to numbers in text file

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Add leading decimal places to numbers in text file

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