search pattern without using built -in function

how to search pattern without using regexp or strcmp function.... that is if i have a word "mississippi" the string "issi" "ssi" "ss"..... occurs two times.... how to write it in code without using built-in function..... how to search whether a particular pattern is in the word and its occurance without using built-in function...... please do reply.....

[Daniel Shub]

What have you tried so far?

Answer 1

[Sean de Wolski]

doc regexp

[Elysi Cochin]

sir but regexp is a built-in function..... is it possible to do without any built-in function?? please do reply.....

Answer 2

[Jan]

Sorry, without built-in functions you cannot perform any useful operations in Matlab. Even the assignment using the "=" operator is a built-in function.

See Answers: What can be programmed without built-in functions

[Elysi Cochin]

sorry sir... i didnt mean all built-in functions.... but those like strcmp and regexp..... only those i meant not to use......

[Elysi Cochin]

sir i have an output as below.... BWM a 12*12 char array....

    BWM =

    $agcagcagact
    act$agcagcag
    agact$agcagc
    agcagact$agc
    agcagcagact$
    cagact$agcag
    cagcagact$ag
    ct$agcagcaga
    gact$agcagca
    gcagact$agca
    gcagcagact$a
    t$agcagcagac

from this output i want to search the pattern "agca"... where it occurs and how many times..... can you show me using built-in functions???..... if possible can you highlight those portions or draw a bounding box in the output..... please do reply sir.... sir for eg:in the word "agcagcagcagc" if i have to find pattern "agac" i want the output *agca*gcagcagc, agc*agca*gcagc, agcagc*agca*gc

but when i use regexp i get only

startIndex =

     1     7

please if possible can you help me to solve this also.....

i did as below...

    k = 1;
    expression = 'gca';
    for i = 1 : 12
        startIndex(1, k) = regexp(BWM(i),expression)
        k = k + 1;
    end

but i'm getting error....

    ??? Subscripted assignment dimension mismatch.

    Error in ==> usage_BurrowsWheelerTransform at 16
        startIndex(1, k) = regexp(BWM(i),expression)

 please do reply.....

[Jan]

I do not have any chance to guess, what built-in function belong to "those" functions, and which are allowed. Are you looking for the term "agca" in horizontal, vertical and diagonal directions? How do you think could the occurrences be "highlighted"? This might be an overly complicated method.

You get the error message, because REGEXP finds multiple occurrences, and you want to store them in a scalar element.

What about a dull FOR loop through the vectors and comparing the parts of the strings by isequal()?

[Elysi Cochin]

sir neednt look to my code.... i know its wrong.... please can you post the correct coding sir??.... please do reply....

[Cedric]

The way you are using REGEXP makes it return an array of starting positions of the pattern in the array of characters that you are passing as a first argument.

You seem to have defined BWM as a rectangular array of characters, why? As Jan mention, should we understand that you have to find vertical occurrences or should we read BWM horizontally as if it were one long string? If such case, you could redefine it as

 BWM = BWM(:).' ;

in order to make it easier for us to understand that it is just one long string and to simplify further processing

Now let's admit that it is just one long string, could you exploit a FOR loop like the following for searching the pattern?

 for k = 1 : length(BWM)-length(expression)+1
    % do something
 end

If you have to "highlight" matches by framing them with stars, you could for example build a second BWM while you read the first, which would include the stars (might be easier than try to insert stars in the current version).

[Elysi Cochin]

thank u all