Reading a select number of characters from a string

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Louis
Louis 2011-12-25
评论： Kiana Maillet 2022-8-15
How would I go about taking the first 5 characters of a string? I want to be able to take a string like "some_string" and take the first 5 characters so I get a new string "some_". I am not sure where to look in MatLab documentation for this.
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Shikhar Pandey
Shikhar Pandey 2016-7-13
for me this is not working. I am implementing it in a callback function in GUI.
Johann Alban Schöpfer
Johann Alban Schöpfer 2018-1-26
If you are reading this in the glorious time of the string data type, you can use the answers below by going back to a char array.
str = "I want to edit this string";
temp = char(str);
% do the things
str = string(temp);

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回答（5 个）

Junaid
Junaid 2011-12-25
Dear Louis,
Let say you have string Variable a;
a = 'HelloMoto';
if you want to take first 5 character of this. It is straight forward.
b = a(1:5); % now b has a's first characters only.
Similarly if you have array of String like this;
A = {'String1', 'String2','String3' };
Then taking string2 as your "Some_String" and then take first 5 character would be like this.
B = A{2};
B(1:5)
I hope this is what you asked for ? Do let me know in either case.
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Louis
Louis 2011-12-25
Message is just read in from an Excel file. It is only a string I am reading in. I tried your suggestion, but that didn't work. Might one issue be that the first 3 characters for some of the actual message in the spreadsheet are spaces?
Kiana Maillet
Kiana Maillet 2022-8-15
Isn't 'that' a character array? and "this" would be a string..

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Jurgen
Jurgen 2019-12-16
If you don't want to convert to char type: extractBetween and it's brethren work on the newer string datatype.
Junaid
Junaid 2011-12-25
Dear Let say your file name is "someFile.xls" then following code should work.
[m mess] = xlsread('someFile.xls', 1);
The size of mess with be number columns and rows in sheet one. Lets assume that in first row second colum there is your requires string you want to take first three initial characters. Then this code should work.
a = char(mess(1,2)); % now a contains that string
myStr = a(1:3); % this should return your first three characters.
Try and let us know, if it works. For experiments you make your own xls file so that you put the string you want. Once the code works and give desired resutls then it would be easy for you to debug your problem in your current xls file, as you mentioned due to spaces or anything.
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Jan
Jan 2011-12-25
"mess{1,2}" is more efficient than "char(mess(1,2))".
Jan
Jan 2011-12-25
@Louis: The white space characters do not cause troubles, because they are characters. But if the strings have less than 3 characters, "a(1:3)" will fail.

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Jan
Jan 2011-12-25
This crops the first 3 characters, but dos not touch shorter strings:
[~,message] = xlsread('someFile.xlsx', 1, entryF);
a = message(1:min(3, length(a)));
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Calum
Calum 2014-11-4
编辑：Calum 2014-11-4
How would I keep only the first three characters from every row in a column of unknown length?
Thanks

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Vahidreza Jahanmard
If you have string format (not char format), you can use this function:
newStr = extract(str,pat)
https://mathworks.com/help/matlab/ref/extract.html

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