Export results from several excel files into one excel file

Hi,

The plan of my code is this: I want to import several xlsx files. Afterwards I do some calculations. This calculations lead to one line of results for each file. In the end I want to have one file, with one line for every imported file.

I start in my code with a for loop, so that the calculation is made for all excel files (anzahl_files is the number of imported files):

for xy=1:anzahl_files
    fid_in=fopen(char(filename(xy)),'r');

Afterwards I import the data and do some calculations (not so interesting for the question):

tmpImport = importdata(filename{xy},','); 
SP_RL = tmpImport.Tabelle1;
SP_RL = regexprep(SP_RL,'\''',''); 
SP_RL = string(SP_RL);

[NumRows NumCols]=size(SP_RL);
Anzahl_Partikel_RL= NumRows;

for m=1:anzahl_elemente
idx = strfind(SP_RL, element_V_RL(:,m));
idx = find(not(cellfun('isempty', idx)));
Elementanzahl_RL(:,m) = length(idx);
end

Now I have with Elementanzahl_RL my final line. Which I want to export now in one file, row after row into a new file. Therefore I tried to have a for loop like this:

for j=1:anzahl_files
Partikel_RL(j+1,:)=Elementanzahl_RL(j,:);
end
end

Anzahl_files is my number of files, which I imported. The second end in this part, is for the first for loop. But sadly its not working and gives me following error:

Index in position 1 exceeds array bounds (must not exceed 1).

Error in TOF_Skript_SingleParticlesgesamt (line 81)
Partikel_RL(j,:)=Elementanzahl_RL(j,:);

I dont find my mistake, does somebody has an idea?

Answer 1

[Raghava S N]

Hi @Tatjana Mü,

Before the loop

for xy=1:anzahl_files
    .
    .
end

You can pre-allocate the matrix "Partikel_RL" with zeros like this:

Partikel_RL = zeros(anzahl_files, anzahl_elemente);

Read more about preallocation here - https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

Now, after this, you can store the final line result of each excel file in "Partikel_RL" like so:

Partikel_RL(xy,:)=Elementanzahl_RL;

There is no need for a loop, as this operation is vectorized.

for j=1:anzahl_files
Partikel_RL(j+1,:)=Elementanzahl_RL(j,:);
end
end

The above loop can be removed.

After the outer xy loop ends, each final line result of each of the excel files will be a row in the "Partikel_RL" matrix.

This matrix can then be written into a single excel file like this:

writematrix(Partikel_RL,'Results.xlsx')

For more details about writing MATLAB arrays to excel files, refer to this link - https://www.mathworks.com/help/matlab/ref/writematrix.html#:~:text=25%092%099-,Write%20Matrix%20to%20Spreadsheet%20File,-Write%20Matrix%20to

Hope this helps!