How to print an array with same column starting locations?

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Bob Thompson
Bob Thompson 2018-2-1
评论： Jos (10584) 2018-2-1
I have an array with varying size data values:
A = [ 1.1 2.123 3.12
1 45.1234 567
1.23 -3.1 7.34567]
I would like to print the array to a file so that it displays with a flush column starting location as shown. I don't mind going line by line through a for loop, but the size of the array is open to variance, so I cannot go manually line by line.
I have tried using %f designation within fprintf, but this fixes the location of the decimal rather than the first character. I have also tried %e and %g as I don't mind having extra zeroes at the end, however, these two do not properly account for the negative value as shown below.
for I = 1:3
fprintf(file,'%1.6e %1.6e %1.6e\n',A(I,:));
end
1.100000e+00 2.123000e+00 3.120000e+00
1.000000e+00 4.512340e+01 5.670000e+02
1.230000e+00 -3.100000e+00 7.345670e+00
Is there some command other than fprintf which can perform this output, or is there some setting within fprintf which can produce the consistent column locations I would like?

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Jos (10584)
Jos (10584) 2018-2-1
Something like this? You can specify left alignment using the - sign
fprintf([repmat('%-12.4f',1,size(A,2)) '\n'], A.') % note the transpose
  2 个评论
Bob Thompson
Bob Thompson 2018-2-1
Ok, yes, this gives what I'm looking for, but I want to make sure I understand what it is doing. I'm assuming repmat means "represent matrix" where each value is a floating number with twelve spaces and four decimal spaces (%12.4f). You indicate that the - sign (%-12.4f) causes an alignment left.
What do the 1 and 2 mean, and why does the array need to be transposed? Also, how would I go about doing something like this with a single line from the array?
Jos (10584)
Jos (10584) 2018-2-1
The '%-12.4f' is a format specifier for fprintf, meaning that it will take a number, print it using 12 positions, aligned to the left ('-') and with 4 decimal positions.
All the other things are just tricks to make it a one-liner. For readability you could consider a double for loop:
for r = 1:size(A,1) % loop over rows
for c = 1:size(A,2) % loop over columns
fprintf('%-12.4f', A(r,c)) ; % print single element
end
fprintf('\n') ; % new line after each row
end
repmat means REPeat MATrix.

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