Error-checking in a matrix

Solved!

Answer 1

[Geoff Hayes]

Salima - try stepping through your code (with the debugger) to see what is going wrong. Look at the first if condition

 if data(1,1:c)==-1

Note that data(1,1:c) is a vector of four elements because you are asking for all elements in the first row. This vector can never be equal to negative one, and so always returns false. Change the condition to

 if find(data(1,:)==-1)

or

 if any(data(1,:)==-1)

Re-run the code with the above change and see what happens!

[Salima]

Thanks a bunch Geoff! If the last row contains corrupted measurements (element -1),then delete all rows with corrupted measurements and print a warning. Firstly I try to find if the last row cointains -1 and if so delete all of the rows cointaing -1. Else replace -1 with next valid measurement.

I have tried the following code, but it doesnt seem to delete the rows with the element -1:

[r , c] = size(data);
        if any(data(r,:)==-1)
            data(any(data==-1,2),:) = []
        else
         for r = r:2
            for c= 1:c
                if data(r,c)==-1
                    data(r,c)=data(r-1,c)
                end
            end
         end

[Geoff Hayes]

Salima - I ran your code with the data initialized as in your question and it was able to remove all of the rows with a negative one. Try stepping through the code and see where it is going wrong.

You are missing an end from your code, so you will need to add it.

[Salima]

Dear Geoff My bad - I forgot to copy the last line with "end" in the comment. Even if I run the following

   [r , c] = size(data);
          if any(data(r,:)==-1)
              data(any(data==-1,2),:) = []
          else
           for r = r:1
              for c= 1:c
                  if data(r,c)==-1
                      data(r,c)=data(r-1,c)
                  end
              end
           end
          end

It doesn't delete the row with -1. It still saves data with the rows with -1 in the workspace.

[Geoff Hayes]

Salima - please post your example data matrix. If it is a large matrix, then just attach it as a mat file (so save the variable to file as save('myData.mat','data') then use the paperclip button to attach this file.

Or step through the code with the debugger to see what is going wrong.

[Geoff Hayes]

Salima - I'm not sure what the format is for the file you attached; it isn't a csv file.

As for the else block code, you should name your indices differently from those two variables, r and c that are the number of rows and columns in your matrix. If you want to move backwards from the last row, you need to specify the step size as a negative one.

 [r , c] = size(data);
 if any(data(r,:)==-1)
     data(any(data==-1,2),:) = []
 else
    for u=r-1:-1:1
        for v=1:c
            if data(u,v)==-1
                data(u,v)=data(u+1,v)
             end
        end
    end
 end