how to parse text file read into cell array

I'm trying to programmatically update a Qspice netlist. I read the *.net file in using fileread.

netlist = fileread([filepath filename);

the file looks like this:

'* netlist
        
     L5 N08 0 {Lp} Rser = 0.01 ic=0
     L6 0 N07 {Ls} Rser=0.01 ic=0
     C3 N06 N08 {Cp}
     C4 N07 N09 {Cs}
     V2 N06 0 pulse -VGA VGA 0 3n 3n period/2 period ac=1
     R1 N09 0 .01
     L1 N11 0 {Lp} Rser = 0.01 ic=0
     L2 0 N10 {Ls} Rser=0.01 ic=0
     C1 N05 N11 {Cp}
     C2 N10 N12 {Cs}
     V1 N05 0 pulse -VGA VGA 0 3n 3n period/2 period
     R2 N12 0 5
     .tran 0 {duration} {starttran} 2n
     .param fres1=83000
     .param period= 1/fsw
     .param Cp = 1/(Lp*(2*pi*fres1)^2)
     .param Lp= 34µ
     .param Ls= 34µ
     .param Cp2 = Cp*2
     .param Idc = 104.42
     .
     .param  Vbat  = 400
     .param RL = Vbat/Idc
     .param Rac = 8/pi^2*RL
     .param Cs2 = Cs*2
     .param Cs = 1/(Ls*(2*pi*fres2)^2)
     k1  L5 L6 {kcoup}
     .param duration =20m
     .param starttran = duration-4m
     .param VGA =40
     .param kcoup=0.2
     .param fres2=85000
     .save I(L5) I(L6) v(n05) i(L1) i(R2)
     k2  L1 L2 {kcoup}
     .param startfreq = 82000
     .param stopfreq = 87000
     .param stepfreq = 50
     .step param fsw list 81750 83000 85000 86400
     .end
     '

fileread brings this in as one big character array.

I want to programmatically replace the .step param line with a new one, as a loop through my code and update some of these parameters.

I can find the index into the char array where ".step param" occurs, but I can't figure out how to convert the characters from .step to the end of that line to a string so I can just replace the whole line with a new one, or to smartly count the characters from .step to the end of that line (those characters change, so I can't just look for a match) and just replace those characters in the array.

Thanks in advance for the help.

Answer 1

[Voss]

filepath = '.';
filename = 'test.txt';

netlist = fileread(fullfile(filepath,filename));

% show the last part of netlist
disp(netlist(1003:end))

     .param startfreq = 82000
     .param stopfreq = 87000
     .param stepfreq = 50
     .step param fsw list 81750 83000 85000 86400
     .end
     

new_stuff = '!!! HERE IS THE MODIFIED LINE - PUT WHATEVER YOU WANT HERE !!!';

netlist = regexprep(netlist,'\.step param.*',new_stuff,'dotexceptnewline');

% show the last part of netlist
disp(netlist(1003:end))

     .param startfreq = 82000
     .param stopfreq = 87000
     .param stepfreq = 50
     !!! HERE IS THE MODIFIED LINE - PUT WHATEVER YOU WANT HERE !!!
     .end
     

[Jorge]

works like a charm!! thank you!

[Voss]

You're welcome!