Why does NUM2STR ignore the width specifier in MATLAB 7.8 (R2009a)?

When I use a format specifier with NUM2STR, it ignores the width specifier. For example the following code returns '1.345' instead of ' 1.345'.

s = num2str(1.345, '%10.3f')

Answer 1

[MathWorks Support Team]

This is expected behavior. The documentation of the NUM2STR function states the following:

"num2str removes any leading spaces from the output string."

To work around this issue, use the SPRINTF function instead. Please see the following examples.

% Example 1.

s = sprintf('%10.3f', 1.345)

% Example 2.

y = [1.0 10.0 100.0]

sprintf('%10.2f\n', y)

% Example 3.

a=[1111.111 22.2222 33.33; 444.4    555.55  66.0];

for i=1:2

    y=sprintf('%-7.3e \t %-6.4e \t %-5.1e',a(i,1),a(i,2),a(i,3))

end

% Example 4.

A = pi*100*ones(1,5);

sprintf(' %f \n %.2f \n %+.2f \n %12.2f \n %012.2f \n', A)

Which outputs the following:

 ans =

     314.159265       % Display in fixed-point notation (%f)

     314.16           % Display 2 decimal digits (%.2f)

     +314.16          % Display + for positive numbers (%+.2f)

           314.16     % Set width to 12 characters (%12.2f)

     000000314.16     % Replace leading spaces with 0 (%012.2f)