Importing big .ASC file

Question

Guglielmo Giambartolomei 2020-7-30

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/572722-importing-big-asc-file

评论： Guglielmo Giambartolomei 2020-8-3

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Good morning, I searched on the web but I din't find anything useful for me.

I have a big .ASC file that begins like this:

Time  1 - default sample rate [s]	MX840A_0_CH 1 [µm/m]	MX840A_0_CH 2 [µm/m]	MX840A_0_CH 3 [µm/m]	MX840A_0_CH 4 [µm/m]	MX840A_0_CH 5 [µm/m]	MX840A_0_CH 6 [µm/m]	MX840A_0_CH 7 [µm/m]	MX840A_0_CH 8 [µm/m]	Time  2 - default sample rate [s]	Time  2 - fast sample rate [s]	MX410_0_CH 1 [µm/m]	MX410_1_CH 2 [g]
0	0,1980	0,3258	-0,2376	-0,5230	1,680	-0,1286	-0,3765	-0,2802	0	0	0,2373	-0,00105	
0,00083	0,07124	0,3033	-0,04901	-0,4132	1,524	0,05268	-0,2449	-0,1356	0,00083	0,00021	0,2639	-0,00067	
0,00167	0,05543	0,2692	0,05971	-0,3727	1,215	0,2908	-0,1258	-0,1223	0,00167	0,00042	0,3119	0,000	
0,00250	0,1738	0,2790	0,2098	-0,3734	0,7158	0,1389	-0,1260	-0,1299	0,00250	0,00063	0,3839	0,00058	
0,00333	0,2204	0,2843	0,3669	-0,2345	0,3564	0,09048	0,01820	-0,04594	0,00333	0,00083	0,3732	0,00080	

...

It is basically n x 13 matrix with a big "n" (millions of rows).

I would like to import all these data in a suitable file for Matlab. I tried with the code:

filename = 'myfile01.txt';
delimiterIn = ' ';
headerlinesIn = 1;
A = importdata(filename,delimiterIn,headerlinesIn);

The result of this simple script (A) is only a 1x1 cell. I can't understand what I am missing. I would like to handle this data in Matlab then, in order to perform an analysis.

Thank you for your help!

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Guglielmo Giambartolomei 2020-7-30

@Ive Ive: no, I didn't try. Thanks!

Guglielmo Giambartolomei 2020-7-30

@Walter Roberson: I'm able to read the text file with the Matlab button "Import data" on the top of the window but it's very slow on my computer.

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Answer 1

Walter Roberson 2020-7-30

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链接

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https://ww2.mathworks.cn/matlabcentral/answers/572722-importing-big-asc-file#answer_473092

在 MATLAB Online 中打开

T = readtable('big.ASC','filetype','text', 'decimal', ',');

(I'm not sure why it loses the variable names.)

When I copy and paste from what you posted, I end up with an empty 14th column, indicating that there is a tab after the 13th column. You can do

T{:,1:13}

to extract a numeric array of 13 columns, or you can

T(:,14:end) = [];

to delete anything after column 13.

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Guglielmo Giambartolomei 2020-7-31

R2018b Walter. Thank you!

Walter Roberson 2020-7-31

I think the above code might work. I am not certain, as the sample you copyied and pasted might not have exactly the same format as your actual file. Testing would be easier if you could attach a sample as a file.

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Answer 2

Guglielmo Giambartolomei 2020-7-31

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https://ww2.mathworks.cn/matlabcentral/answers/572722-importing-big-asc-file#answer_473407

Dear Walter, I downloaded the 2020a version and it works! I have a question: now I have a n x 1 table (one column of the T table). How can I covert that object in a n x 1 double in order to analyse the data? Thank you!