How to identify a string and copy the value from the text file

Hii ppl... can anyone suggest how to identify a string in a txt file... im using some instructions and it is working well... if a string something like 151.04 LMD[q=1,d=2] 99.9972 % .. it has to identify the line of the string and give me the value as 99.9972.. if the string is like 150.04 ROTOR TIMECONST 940 m Im able to get the value as 940.. but the brackets [] are giving me problem.. how to solve this?? please suggest me

Answer 1

[per isakson]

This script

    str = fileread( 'cssm.txt' );
    cac = regexp( str, '(?<=LMD\[q=1,d=2\][ ]+)[\d\.]++(?=[ ]+\%)', 'match','once' )
    cac = regexp( str, '(?<=ROTOR TIMECONST[ ]+)\d++(?=[ ]+m)'    , 'match','once' )

returns

    cac =
    99.9972
    cac =
    940

where cssm.txt contains

    Hii ppl... can anyone suggest how to identify a string 
    in a txt file... im using some instructions and it is 
    working well... if a string something like
    151.04 LMD[q=1,d=2] 99.9972 % .. it has to identify 
    the line of the string and give me the value as 99.9972.. 
    if the string is like 150.04 ROTOR TIMECONST 940 m Im able 
    to get the value as 940.. but the brackets [] are giving me 
    problem.. how to solve this?? please suggest me

Mostly, regex is fast enough

&nbsp

ADDENDUM

The script below does the "same" job orders of magnitude faster. (I guess, I did a beginners mistake.)

    str = fileread( 'cssm.txt' );
    cac = regexp(str, '(?<=LMD\[q=1,d=2\])[ \d\.]++(?=\%)', 'match','once')
    cac = regexp(str, '(?<=ROTOR TIMECONST)[ \d]++(?=m)'  , 'match','once')

returns

    cac =
     99.9972 
    cac =
     940

The differences are that in this latter case

• the spaces, which surrounds the value, are captured together with the value.
• if there is only spaces between "ROTOR TIMECONST" and "m", this script captures the string of spaces
• ...

This variant doesn't capture a string of spaces

    cac = regexp(str, '(?<=ROTOR TIMECONST) +\d++ +(?=m)', 'match','once')

but is significantly slower.

[madhu T S]

thank you so much per isakson... the given code is working perfectly.. thanks again

[madhu T S]

Hi its taking long time to get the value... is there any other way to get the value??

thanks and regards Madhu

[per isakson]

Yes, but faster .... . What's the fastest way depends heavily on the size and content of the file. BTW: what do you mean by slow?

I've added a faster script to my answer.

[madhu T S]

Hi per isakson... actually slow in the sense... if I use the code to get the value once its working fine... i have 60 lines of data in which the braces [] present.. it taking long time to process these 60 lines and to give value for these 60 lines...

Answer 2

[the cyclist]

Here is one way, assuming that the value you are looking for is always between two spaces at the end of the string:

S = '150.04 ROTOR TIMECONST 940 m';

% Find where the spaces are
indexToSpaces = regexp(S,' ');

% Get the characters that are between that last two spaces
valueString = S(indexToSpaces(end-1)+1:indexToSpaces(end)-1);

% Convert those characters to numeric
value = str2double(valueString);

If that is not correct, then you need to think carefully about what rule will consistently identify where the value is. Then maybe we can help you translate that into MATLAB code.

[madhu T S]

thanks for your answer the cyclist, Im using the same logic but its working for others except for 151.04 LMD[q=1,d=2] 99.9972 %, the sqare brackets making problem for the above code... However I got code from per isakson and its working well... thanks again for your feed back the cyclist