Insert two text lines in the blank rows of a txt file

I have to insert two different text rows in the blank rows of the attached txt file. How should I proceed?

[KSSV]

You want to insert in the existing file? You can do that while creating the file itself right?

[Emilio Pulli]

I would prefer to insert in the existing file...however, the attached file is created in the code that I am writing but it requires to respect certain format specs and I do not want that inserting text lines during the creation will affect the format specs of the file itself.

At the moment, while I am creating the file, I am inserting 2 rows of NaN everytime that a numeric sub matrix ends. Afterthat, I replace the NaN rows with blank spaces and I write the txt file. If there is a method, according to which, I can write the two text rows in spite of the two NaN rows, it could be helpful, but I need that the format specs of the numeric cells is not affected!

Here, there is my code:

v_cutin=2.5;
v_cutout=15;
v_rated=5.5;

v=linspace(v_cutin,v_cutout,15);

D=2.5;
R=D/2;
r=linspace(0.15*R,R*0.97,100); 

omega_rpm=linspace(1,600,200);

dataset=importdata('dataset.mat');
dataset_red=NaN*ones(((length(omega_rpm)/10)+1)*length(v)+length(v)-1,6);
x=1;
row=0;
y=3;
stop=0;
start=0;

for i=1:length(dataset)
    if start==0
        dataset_red(1,:)=NaN*ones(1,6);
        dataset_red(2,:)=NaN*ones(1,6);
        start=1;
    elseif isnan(dataset(i,1))==0 && start>0
        row=row+1;
        stop=0;
    elseif isnan(dataset(i,1))==1 && stop<1 && start>0
        step=floor(row/10);
        check=mod(row,10);
        if check==0
            dataset_red(y:1:y+9,:)=dataset(x:step:(i-1),:);
            dataset_red(y+10,:)=NaN*ones(1,6);
            dataset_red(y+11,:)=NaN*ones(1,6);
            x=i+1;
            row=0;
            y=y+12;
        elseif check>0
            dataset_red(y:1:y+10,:)=dataset(x:step:(i-check),:);
            dataset_red(y+11,:)=NaN*ones(1,6);
            dataset_red(y+12,:)=NaN*ones(1,6);
            x=i+1;
            row=0;
            y=y+13;
        end
            stop=stop+1;
    elseif stop==1
        i=length(dataset);
    end
end

A=dataset_red;
fmt = "%8.3f";
S = standardizeMissing(compose(fmt, A), "     NaN");
writematrix(S, 'dataset_red.txt', 'delimiter', 'tab');

[KSSV]

You can use fprintf in the loop where you are generating the data. Give a condition and put text when condition is met. Read about fprintf.

[Emilio Pulli]

fprintf write the data also in the matrix?

Answer 1

[Jan]

You cannot insert text in files, because a file an grow at its end only. There is no operation to shift the contents of a file.

You have to import the file at first, insert the data, and recreate the file. Prefer an import as text to avoid rounding effects with the limited precision of the input.

By the way, this can be simplified:

dataset_red(y+10,:)=NaN*ones(1,6);

% Version 1:
dataset_red(y+10,:) = NaN(1,6);

% Version two using Matlab's expanding of scalars:
dataset_red(y+10,:) = NaN;

This will not work:

for i=1:length(dataset)
   ...
   if <anycondition>
      i = length(dataset) 
   end
end

Matlab's for command does not care about the value of the counter. See:

for k = 1:5
   disp(k)
   k = 17;
end
% This prints: 1 2 3 4 5

Either convert the loop to a while loop or use break to stop the loop.

if start==0
    dataset_red(1,:)=NaN*ones(1,6);
    dataset_red(2,:)=NaN*ones(1,6);
    start=1;
elseif isnan(dataset(i,1))==0 && start>0    

After you have excluded the case start==0 already, there is no need to check for start>0 again.

[Emilio Pulli]

ok thank you man but the main problem of inserting the text lines remain....

[Emilio Pulli]

I figured it out by manipulating te string matrix S in this way:

%% [...] The code previously typed till the creation of string matrix S
flag=0;
for i=1:size(S,1)
    for j=1:1:size(S,2)
        if ismissing(S(i,j))==1 && j==1 && flag==0
            S(i,j)={'Variables = v_wind[m/s],omega[rpm],Cp,Cm,P[W],M[Nm]'};
            flag=flag+1;
        end
        if ismissing(S(i,j))==1 && flag==1 && j==1
             S(i,j)={['ZONE T = “V wind =',num2str(S(i+1,1)),'[m/s]”']};
             flag=0;
        end
    end
end
writematrix(S, 'dataset_red.txt', 'delimiter', 'tab');