How do I use fprintf to show the entire array in one ouput statement

>>

A = [-4 2 -7 6 8; 4 -5 8 -1 0; 0 -4 3 1 10; -8 7 -10 5 -2];

[rows cols] = size(A);

Z = zeros(size(A));

for x = 1:1:rows

    for y = 1:1:cols
        if A(x,y) <= 4
            Z(x,y) = A(x,y);
        end
    end
end

fprintf('%i\n',Z);

My ouput statement I am getting is

   -4
         4
   0
  -8
   2
  -5
  -4
   0
  -7
   0
   3
  -10
   0
  -1
   1
   0
   0
   0
   0
  -2

Instead of

                         -4   2 -7   0  0

                          4  -5  0  -1  0   

                          0  -4  3   1  0

                         -8   0 -10  0 -2

[Stephen23]

A = [-4,2,-7,6,8; 4,-5,8,-1,0; 0,-4,3,1,10; -8,7,-10,5,-2];
Z = A;
Z(Z>4) = 0;
display(Z) % <- much simpler than FPRINTF

Z = 4×5

-4 2 -7 0 0 4 -5 0 -1 0 0 -4 3 1 0 -8 0 -10 0 -2

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Answer 1

[Jan]

fprintf('%i %i %i %i %i\n', Z.');

or:

fprintf('%4i %4i %4i %4i %4i\n', Z.');

Note that the matrix must be transposed, because the elements are store columnwise, but the display is written in rowwise order.

By the way: It is easier without loops:

Z        = zeros(size(A));
index    = (A <= 4);
Z(index) = A(index);

Or:

Z        = A;
Z(Z > 4) = 0;

[Josua Mensah]

Thanks man. Was not even aware of the other ways to go about it.

Answer 2

[Jay Stanley]

Tunc Durmaz,

If you do not know the dimension of your array you can get its size and replicate a template based on those dimensions

Here's a minimum working example

matrix = magic(4) % example matrix
[mrows, ncols] = size(matrix)
outputstr = ['%' num2str(mrows) 'i '] % template for the string, you put your datatype here
outputstr = repmat(outputstr, 1, ncols) % replicate it to match the number of columns
outputstr = [outputstr '\n'] % add a new line if you want
fprintf(outputstr, matrix.') % write it

For completeness sake there is another trivial solution that does not use repmat via the loop

matrix = magic(4) % example matrix
[mrows, ncols] = size(matrix)
outputstr = ['%' num2str(mrows) 'i ']
template = ['%' num2str(mrows) 'i '] % template for the string, you put your datatype here
outputstr = template
for i = 2:mcols
    outputstr = [outputstr template]
end
outputstr = [outputstr '\n'] % add a new line if you want
fprintf(outputstr, matrix.') % write it

[Tunc Durmaz]

That was very helpful, thanks!

[Robert Laws]

You can exploit the fact that sprintf repeats the format. Something like this can work when the data are a vector of unknown length.

ctemp=sprintf('%3i ', someintegervector);

fprintf('This is the content of the vector: %s OK', ctemp));

Answer 3

[Tunc Durmaz]

What if we do not know the dimension of Z? Any way to address this in fprintf?

Cheers,

Answer 4

[Steven Lord]

This wasn't an option when the question was originally asked, but if you wanted to capture the matrix in text exactly as it would be displayed in the Command Window you could use the formattedDisplayText function.

A = [-4 2 -7 6 8; 4 -5 8 -1 0; 0 -4 3 1 10; -8 7 -10 5 -2]

A = 4×5

-4 2 -7 6 8 4 -5 8 -1 0 0 -4 3 1 10 -8 7 -10 5 -2

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s = formattedDisplayText(A)

s = 
    "    -4     2    -7     6     8
          4    -5     8    -1     0
          0    -4     3     1    10
         -8     7   -10     5    -2
     "

Let's say I wanted to cut the spacing between elements in half, replacing two spaces with one. I could manipulate the string s.

s2 = replace(s, "  ", " ")

s2 = 
    "  -4   2  -7   6   8
        4  -5   8  -1   0
        0  -4   3   1  10
       -8   7  -10   5  -2
     "

Or I could add commas after each number except the last:

s3 = regexprep(s, "(\d) ", "$1,")

s3 = 
    "    -4,    2,   -7,    6,    8
          4,   -5,    8,   -1,    0
          0,   -4,    3,    1,   10
         -8,    7,  -10,    5,   -2
     "