MATLAB: How can i replace a line form a text

algorithmprogrammingstringtext file

I have the following text file i want to replace all the line that contains this pattern X = 259.557 mm, Y = 563.173 mm, Z = -104.284 mm,
with a new line that contains the existing numbers added by a certain value.

Best Answer

You can easily match those lines using a regular expression. Something like this:
fmt = sprintf('\\s*%c\\s*=\\s*(\\d+\\.\\d+)\\s*mm,','XYZ')
fmt = sprintf('^%s\\s*$',fmt)
str = fileread('values.txt');
spl = regexp(str,'[\n\r]+','split');
tmp = regexp(spl,fmt,'tokens','once');
idx = find(~cellfun('isempty',tmp));
for k = reshape(idx,1,[])
    vec = str2double(tmp{k}) + 2; % add two as example data manipulation.
    spl{k}  = sprintf(' X = %.3f, Y = %.3f, Z = %.3f,',vec);
end
fid = fopen('newfile.txt','wt');
fprintf(fid,'%s\n',spl{:});
fclose(fid);
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