textscan trouble: starting file position on re-read

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David C 2014-6-19

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https://ww2.mathworks.cn/matlabcentral/answers/136479-textscan-trouble-starting-file-position-on-re-read

编辑： per isakson 2015-5-10

I'm trying to read a data file of integers. The file is formatted as follows:

 -112-999-999-999-555
 -999-999
 -777   0   0   0   0
    0  20
 -757  11   0   0   0
    0   0

There are 3 blocks of 7 numbers each.

I tried

fid=fopen('filename.txt')
textscan(fid,'%4d',7)

And got the following as expected.

-112
-999
-999
-999
-555
-999
-999

But then I issue &nbsp textscan(fid,'%4d',7) &nbsp again. I would expect to get the second block this time, but instead I get:

It seems textscan started reading at the wrong place (not where it left off).

Any thoughts why it's doing this?

Thanks, David

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dpb 2014-6-20

http://www.mathworks.com/support/contact_us/index.html?s_tid=hp_ff_s_contact

Patrick 2014-10-9

I ran into this same issue with R2013b.

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回答（1 个）

Image Analyst 2014-6-20

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https://ww2.mathworks.cn/matlabcentral/answers/136479-textscan-trouble-starting-file-position-on-re-read#answer_141725

In your second call to textscan() your first argument is fww. What is that? Why are you not using fid like in the first call to textscan()????

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Stephen23 2014-10-10

编辑：Stephen23 2014-10-10

Tested with MATLAB R2012b. I downloaded your data file filename.txt, and ran the following code:

>> fid = fopen('filename.txt');
>> A(1) = textscan(fid,'%4d',7);
>> A(2) = textscan(fid,'%4d',7);
>> fclose(fid);
>> [A{:}]
ans = 
        -100        -106
        -101         107
        -102         108
        -103           0
        -555           0
        -104           0
        -105          20

This seems to give the outputs you want.

per isakson 2015-5-10

编辑：per isakson 2015-5-10

With 2014a

    ans =
            -100           0
            -101        -101
            -102        -102
            -103        -103
            -555        -555
            -104        -104
            -105        -105

was this ever reported?

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