How to discard all punctuation from a text file

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Fateme Jalali
Fateme Jalali 2016-1-18
评论： Image Analyst 2017-9-16
Hello, I need a MATLAB code to discard all punctuation and signs from a text file.I want to keep only characters and numbers.Thanks.

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采纳的回答

John BG
John BG 2016-1-19
Star Stride is right but perhaps Fateme wants to keep the spaces, because space is not punctuation spaces will help reading the resulting string. The initial string
str1 = 'Hello, I need 1 MATLAB code to discard all punctuation, and signs from 9 text files.'
Lstr1=length(str1)
the characters that have to remain are
str_space='\s'
str_caps='[A-Z]'
str_ch='[a-z]'
str_nums='[0-9]'
their respective positions within str1 are
ind_space=regexp(str1,str_space)
ind_caps=regexp(str1,str_caps)
ind_chrs=regexp(str1,str_ch)
ind_nums=regexp(str1,str_nums)
mask=[ind_space ind_caps ind_chrs ind_nums]
now let's find the position of all punctuation characters
num_str2=1:1:Lstr1
num_str2(mask)=[]
now num_str2 contains the positions of punctuation characters to remove
str3=str1
str3(num_str2)=[]
str3 contains the resulting string without any other character than alphabetical characters and numbers.
str3 =
Hello I need 1 MATLAB code to discard all punctuation and signs from 9 text files
Hope it helps in your reading.
John
jgb2012@sky.com
  1 个评论
Fateme Jalali
Fateme Jalali 2016-1-19
thank you.After discarding all punctuation i want to put a white space before the first character and after the last one.How can i do it?thanks

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更多回答（3 个）

Star Strider
Star Strider 2016-1-18
编辑：Star Strider 2016-1-19
One possible approach:
str = 'Hello, I need 1 MATLAB code to discard all punctuation, and signs from 9 text files.';
Idx = regexp(str, '[^. , !]');
Result = str(Idx)
EDIT — To keep the spaces, just remove them from the regexp pattern string (in this instance, I was telling it to exclude spaces as well as the punctuation):
str = 'Hello, I need 1 MATLAB code to discard all punctuation, and signs from 9 text files.';
Idx = regexp(str, '[^.,!]');
Result = str(Idx)
Result =
Hello I need 1 MATLAB code to discard all punctuation and signs from 9 text files
You can add as many other punctuation or other characters as necessary between the square brackets ‘[]’, depending on what appears in your strings that you do not want in the result.
  2 个评论
Mubashir
Mubashir 2017-9-16
I want to use this in table. I can't remove punctuation's in whole column.
Image Analyst
Image Analyst 2017-9-16
So then go down the table's column one row at a time. What's wrong with that? It's easy.

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Walter Roberson
Walter Roberson 2016-1-19
http://www.mathworks.com/help/matlab/ref/isstrprop.html
https://www.mathworks.com/matlabcentral/newsreader/view_thread/127125
  2 个评论
Fateme Jalali
Fateme Jalali 2016-1-19
thank you.After discarding all punctuation i want to put a white space before the first character and after the last one.How can i do it?thanks

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Image Analyst
Image Analyst 2016-1-19
Yet another way:
str = 'Hello, ~!@#$^&*()_+.,<>;"?I need 1 MATLAB code to discard all punctuation, and signs from 9 text files.'
% Get logical index to keep space, numbers, and upper and lower case letters.
keeperIndexes = str == ' ' | (str>='0' & str<='9') | ...
(str>='a' & str<='z') | (str>='A' & str<='Z');
strOut = str(keeperIndexes) % Extract only those elements

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