When using fprintf to format multiple strings, what does the integer after the % sign do?

Hi,

Given something such as:

fprintf('%5d %10.3f %8.5e\n',100,2*pi,pi);

What do the numbers directly after the % sign do? I understand that %5d displays an integer, 5 spaces in from the beginning of the line. But, I don't understand what the %10 does. I know the .3f says to display decimal format with 3 decimal places, but what does the 10 do? And what does the %8 do? If I type

fprintf('%5d %3.3f %8.5e\n',100,2*pi,pi); or fprintf('%5d %4.3f %8.5e\n',100,2*pi,pi);

I get the same answer. It isn't until I get to

fprintf('%5d %6.3f %8.5e\n',100,2*pi,pi);

That the spacing changes, and then the spacing increases by 1. So, I see that it seems to be related to the previous spacing argument, but I can't figure out the exact pattern. Clarification would be greatly appreciated. Thank you!

Answer 1

[Shashank Prasanna]

It is the field width or the minimum numbers of characters to print.

Check this link out:

http://www.mathworks.com/help/matlab/ref/fprintf.html#inputarg_formatSpec

scroll down for a diagrammatic representation and explanation.

[Matthew Cooper]

Thank you for the link, but I don't think it's as simple as saying that it is the field width or the minimum numbers of characters to print. If you notice in the example I provided, the second argument seems to depend on the first argument, e.g. %10.2f, %5.3d will produce the same thing as %10.2f, %6.3d and also the same as %10.2f, %7.3d...it doesn't change the spacing until I get to %10.2f, %11.3d. It's as if the second argument has to be greater than the first.

[Jan]

As the documentation explains accurately, the value before the dot is the "field width", and the value after the point the "precision". If a number has more digits, caused by its value and the precision, than allowed by the field width, more digits are written. This means, the first value is a "minimal field width" and spaces are used for padding on demand.