How to discard all punctuation from a text file

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.

Answer 1

[John BG]

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

[e-mail]

[Fateme Jalali]

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

Answer 2

[Star Strider]

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.

[Mubashir]

I want to use this in table. I can't remove punctuation's in whole column.

[Image Analyst]

So then go down the table's column one row at a time. What's wrong with that? It's easy.

Answer 3

[Walter Roberson]

http://www.mathworks.com/help/matlab/ref/isstrprop.html

https://www.mathworks.com/matlabcentral/newsreader/view_thread/127125

[Fateme Jalali]

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

[Walter Roberson]

YourString = [' ' YourString ' '];

Answer 4

[Image Analyst]

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