Make my code for taking norm efficient

here is my code that is taking norm between 2 rows from 2 different excel files,it picks one row from my_first_file.xlsx and take norm with all the rows in my_second_file.xlsx and and store all the values to R i.e array/ vector and after completing one inner loop it takes the minimum value and its index from the array R,it runs OK but it takes lot much time to execute,please amend it in such a way that it takes considerably less time and performs efficiently and correct me where i am wrong,you are welcome.

n=853;m=500;
for s=1:n   % n=number of rows in my_first_file.xlsx
filename = 'my_first_file.xlsx';
row1 = xlsread(filename,strcat('E',num2str(s),':EB',num2str(s)));

for i=1:m % m=number of rows in my_second_file.xlsx

      filename1 = 'my_second_file.xlsx';
      row2 = xlsread(filename1, strcat('A',num2str(i),':DX',num2str(i)));

      sqE=norm(row2-row1);
      R(i) = sqE;

end

      [Val Ind] = min(R);
      ran=sprintf('%c%d','A',s);
      xlswrite(Hello, [Val, Ind],resultsheet,ran);
  end

Answer 1

[Mischa Kim]

Muahmmad, why don't you read in all data from the Excels files at once (in other words you are only calling xlsread twice) and save the data in matrices? If available (Parallel Computing Toolbox, that is), use parfor instead of a for-loop.

[Muhammad Usman]

i don't know how to read the data from matrix row-by-row... if u know please guide me i ll check

[Mischa Kim]

Use something like

 mat1 = xlsread('ex1.xlsx');   % define the range for your files appropriately
 mat2 = xlsread('ex2.xlsx');   % define the range for your files appropriately

 for ii = 1:size(mat1,1)
    for jj = 1:size(mat2,1)
        norm_12(jj + (ii-1)*size(mat2,1)) = norm(mat1(ii,:)-mat2(jj,:));
    end
 end

[Muhammad Usman]

I draw some results using my code,and then i try your above code i got different values please explain me if u can that what does this means

norm_12(jj + (ii-1)*size(mat2,1))

Answer 2

[Joseph Cheng]

before the for loop read all the data from row 1 to row m from my_second_file.xlsx into matlab and then reference that data in the loop. it should reduce the time from opening and reading from the excel file in each for loop.

[Muhammad Usman]

let me know how do i reference... Thanks

[Joseph Cheng]

you basically did so before. just as you're reading in one line at a time. read in the whole thing like Mischa Kim described. so instead of reading in each row read in the whole block

 XLS1= xlsread(filename,strcat('E',num2str(1),':EB',num2str(n)));
 XLS2 = xlsread(filename1, strcat('A',num2str(1),':DX',num2str(m)));

Then you you can reference them like any 2D array in matlab.