Counter Values Are Not Changing, MATLAB

I am new to Matlab and I have an issue where two counters in my code do not change value.

 fid = fopen('results.txt', 'wt');

 counter1 = 0;
 counter2 = 3;

 for i=1:size(res_t,1)

    counter1 = counter1 + 1;

    if(counter2 == 3)
      fprintf(fid, '%f ', res_t.time(:,:)); % first column i need the time
      counter2 = 0;

    end   

     fprintf(fid, '%f ', res_t.data(:,:)');

     if(counter1 == 3)
            fprintf(fid, '\n'); %after it writes all 3 X,Y,Z i want to change line
            counter1 = 0;

     end

     counter2 = counter2 + 1;

 end

 fclose (fid);
}

When compiled, the values of counter1 & counter2 do not change, which means they never meet the If statement conditions. My output file is a file which contains: column1: time values, columns2 to 4: X, Y, Z coordinates respectively.

For example:

Time1 X1 Y1 Z1

Time2 X2 Y2 Z2

Thanks!

Answer 1

[dpb]

Probably because

size(res_t,1)

is either empty or 0 so the loop never executes.

You say "when compiled"; is that a euphemism or are you really building a compiled .exe? I've never had the toolbox so don't know what/how it deals with undefined variables when it finds one--at the command line if res_t didn't exist you'd error and know what the problem is.

[Daniel Barzegar]

no i am not building a compiled .exe. you are right the value of size(res_t,1) = 1 , that's why i doesnt do the loop. res_t is a matrix having 9 lines so i want the loop to execute until the end of it . how can i get that value?

[José-Luis]

This sounds a bit like a contradiction. First you say that size(res_t,1) = 1 and then you say the it has nine lines? How is that possible?

Perhaps you meant size(res_t,2)?

[Daniel Barzegar]

well, my matrix has 9 lines and i want to do the for loop for all the lines. How i can do the for loop until the end of the matrix?

for i=1: ???

... ...

end

cheers

[José-Luis]

By lines you mean row or columns?

Answer 2

[Image Analyst]

Why not just write out all 4 numbers in a single fprintf()???? Also, you'd have to index res_t with i, which you're not doing now.

[Daniel Barzegar]

because this is just a small example . my real file has more than 5000 samples...!

[Image Analyst]

5000 is still pretty small.

Answer 3

[dpb]

...the value of size(res_t,1) = 1 , that's why i doesnt do the loop. res_t is a matrix having 9 lines

Well, one or the other of those statements is just plain wrong. Use the debugger and step thru and figure out where it goes wrong or show enough context we can tell -- as is, there's not enough information to do anything useful on that part.

Oh, I see...you've written

for i=1:size(res_t,1)

but it turns out looking on down later that res_t is a structure not matrix. You need

for i=1:size(res_t.data,1)

to address the data array inside the structure.

And, as IA indicates, why not write the file with one of the higher-level routines like dlmwrite or at least with a single fprintf loop?

dlmwrite('yourfile',[res_t.time res_t.data], 'delimiter', ' ')

[Daniel Barzegar]

yes, you are right. i just had to have size(res_t.data). thanks!