Padding flag of the formatting operator in compose()

I am trying to get my head around to how the padding flag works. For instance, I get:

>> compose("%05d",45)
ans = 
    "00045"

Nevertheless, if I try the same using a formatting operator for floating number, this flag seems to do nothing:

>> compose("%05.2f",45.23)
ans = 
    "45.23"

Why is the result not "00045.23" in this case?

Regards,

Cristian

Answer 1

[Matt J]

Because then the length of the string would be 8 instead of 5.

 compose("%08.2f",45.23)

ans = "00045.23"

Answer 2

[Dyuman Joshi]

The number before the decimal specifies the length/field width of the output string.

Padding will only be there if there is space for it.

sprintf('%0*.2f\n', [6 45.23 7 45.23 8 45.23])

ans = 
    '045.23
     0045.23
     00045.23
     '

sprintf('%0*.3f\n', [7 123.456 8 123.456 9 123.456])

ans = 
    '123.456
     0123.456
     00123.456
     '

[Adam Danz]

Ha! I don't think I've seen this use of sprintf before. It took me a few minutes to figure out that the odd index values of the 2nd argument are space indicators and the even index values the values to be printed. Difficult to read but interesting! Ya learn something new every day! :)

[Dyuman Joshi]

It is an interesting funcitonality!