search pattern without using built -in function

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Elysi Cochin 2013-4-5

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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.....

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Daniel Shub 2013-4-5

What have you tried so far?

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Answer 1

Sean de Wolski 2013-4-5

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在 MATLAB Online 中打开

doc regexp

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Elysi Cochin 2013-4-5

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

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Answer 2

Jan 2013-4-5

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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

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Elysi Cochin 2013-4-6

编辑：Elysi Cochin 2013-4-6

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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.....

Cedric 2013-4-6

编辑：Cedric 2013-4-6

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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 2013-4-8