Search for elements in a string

I am trying to find whether a certain string of letters and special characters ( like /) and then output true if it does and false if it doesn't. I know I should convert the characters to numbers using double() but after that I am not sure what to do. An example would be to see if 'add?/adfd' has any elements from ascii value 32-47.

[Cedric]

Could give an example of text and string that you need to find? There are several tools available, e.g. STRFIND and REGEXP. the former is easy to understand and use, but limited, and the latter is powerful but we would need to know more about the type of strings that you need to find before we can propose a solution.

Answer 1

[Stephen23]

Why make it all complicated with regexp. Keep it simple and very MATLAB with bsxfun :

any(any(bsxfun(@eq,'add?/adfd',[32:47].')))
ans = true

The second input to bsxfun is your string, and the third is a column vector of the ascii values that you want to check for.

Answer 2

[Chad Greene]

For multiple special characters, use a few calls of regexp and any:

s = 'abcd\potatoes\eddie\murphy?martin/lawrence';
specialChars = [regexp(s,'\.') regexp(s,'&') regexp(s,'/') regexp(s,'^')];

if any(specialChars) 
    disp('Yeah, they''re some special characters alright.') 
end

[Cedric]

If the goal is not to extract their positions separately, the following would do:

 pos = regexp( s, '[\.&/^]' ) ;

[Chad Greene]

brilliant!

[Guillaume]

And even, if it is, a single regexp still suffice:

s = 'abcd\potatoes\eddie\murphy?martin/lawrence';
[pos, match] = regexp(s, '[\\?/]', 'start', 'match');
[characters, ~, subs] = unique(match);
positions = accumarray(subs, pos, [], @(p) {p})';
[characters; positions]

Answer 3

[Chad Greene]

Use regexp

s = 'abcd\potatoes\eddie\murphy';
indicesOfSlash = regexp(s,'\')
indicesOfSlash =
     5    14    20

Answer 4

[Image Analyst]

Here's a method that (in my opinion) is a little more intuitive, straightforward, and less cryptic than regexp() and bsxfun():

s = 'add?/adfd' % The starting string
d = s - ' ' + 32   % Convert to ASCII number array
% Get indexes of where d is between 32 and 47
specialCharIndices = find(d >= 32 & d <= 47)

[Bob Whiley]

How can I turn this into a true false logical, like if it has one at position 9 in the string, how can it output 'true'?

[Image Analyst]

logicalIndices = d >= 32 & d <= 47;

[Stephen23]

"a little more intuitive, straightforward, and less cryptic", that is until you want to compare more than one contiguous group of characters:

(s>=32 & s<=47) | (s>=58 & s<=60) | (s>=62 & s<=64) | (s>=133 & s<=140) % etc

bsxfun(@eq,'add?/adfd',[32:47,58:60,62:64,133:140].')

The bsxfun solution is much more robust in comparing any two input vectors, regardless of the contiguity or later decisions about what characters to include/exclude.

Answer 5

[per isakson]

A code based on regexp

    str = 'add\?/adfd';
    chr = char(32:47);
    xpr = ['[',regexptranslate('escape',chr),']'];
    pos = regexp( str, xpr, 'once' );
    has = not(isempty(pos));

This code may be squeezed into one obscure line.

Answer 6

[Stephen23]

How about the simplest solution of all isstrprop, which lets you do something like this all in one line:

>> ~isstrprop('add?/adfd','alpha')
ans =
     0     0     0     1     1     0     0     0     0