A compact way to find single digit numbers (i.e. numbers between 0 and 9) and replace them with two digit numbers

A compact way to find single digit numbers (i.e. numbers between 0 and 9) and replace them with two digit numbers ?

For example, from:

a = [ 8
     12
     15
     76
      3
     99
      0];

I would like to add a zero in front of the single digit numbers:

b = [08
     12
     15
     76
     03
     99
     00];

[Stephen23]

No standard numeric class stores formatting information like leading zeros:

https://www.mathworks.com/help/matlab/numeric-types.html

Most likely you are confusing how data are displayed with what data are actually stored in memory. It is possible that you could select a suitable FORMAT() or write some display routine, but because you did not describe your use-case, you made it much harder for us to help you.

[James Tursa]

"No standard numeric class stores formatting information like leading zeros"

I understand your intended message, but pretty much all integer class variables store leading zero information at the binary level (amount varies depending on number bits of integer), which could be used for leading 0 display purposes but typically isn't.

[Stephen23]

I undestand your intended message, but no integer class stores formatting information, which is specifically what I wrote in my comment. A fixed number of implicit leading zeros due to the fixed number of bits is not formatting information. Even if some meta-data was provided giving such formatting information those stored bits "at the binary level" are completely irrelevant anyway: for example if the user wants fifty digits with leading zeros, then this is always possible, regardless of how many "zeros" the numeric class (explicitly or implicitly) stores:

fprintf('%0.50u\n',uint8(23))

00000000000000000000000000000000000000000000000023

[Sim]

thanks for the explanation! :)

[James Tursa]

"A fixed number of implicit leading zeros due to the fixed number of bits is not formatting information"

My point was that it could be used as very basic formatting info without any additional meta-data involved, by simply printing all significant digits including the leading 0's according to the length of the integer stored. Again, not something typically done but it could be done. This wouldn't provide a way for a user-selectable number of leading 0's, but that wasn't my intended point.

[dpb]

But the number of bits in the storage unit isn't (directly) at all related to the size of the decimal integer able to be stored in the storage unit. While it's not too bad with a byte-wide integer of 8 bits, even there that would imply five leading zeros for a uint8; when you get to 32 or 64-bit integers, it woud be just a wee bit (so to speak :) ) unwieldy.

[James Tursa]

My comments:

"But the number of bits in the storage unit isn't (directly) at all related to the size of the decimal integer able to be stored in the storage unit"

Of course it is, via log2( ). For 2's complement or 1's complement storage it isn't 1-for-1 conversion max value wise of course. For Binary Coded Decimal it would be.

"... five leading zeros for a uint8"

Not sure where this comes from. A uint8 only goes up to 255 with is three total digits.

My final comment is that this side thread has taken on a direction I didn't intend, and I would be happy to delete my initial comment and everything that follows since it is not adding anything to the main discussion. Agreed?

[dpb]

No problem from me...I was just thinking you were suggesting to put the 8-bits of zeros out based on the number of bits, not on the magnitude of the contained value it could hold.

But, agreed, it's taken off on a complete tangent...

[Sim]

I did not think to cause such a fuss :-) ....but the conversation is very interesting, thanks!

Answer 1

[John D'Errico]

In MATLAB, you CANNOT store a number in a numeric format as one that has a leading zero.

If you want to convert the numbers to character form, then it is trivial. One line is sufficient.

a = [ 8
    12
    15
    76
    3
    99
    0];

d = dec2base(a,10)

d = 7×2 char array
    '08'
    '12'
    '15'
    '76'
    '03'
    '99'
    '00'

The result is no longer usable as a number though. It is effectively only a picture of a number at that point, or perhaps I should say a caricature, if you can stand the pun.

[Sim]

Thanks a lot! I would like to accept both of your answers!!!

Answer 2

[dpb]

For what purpose and in what context? You will only be able to show the leading zeros if you convert the numeric values to some form of text in which case it's trivial

>> compose('%02d',a)
ans =
  7×1 cell array
    {'08'}
    {'12'}
    {'15'}
    {'76'}
    {'03'}
    {'99'}
    {'00'}
>> 

Well, there is one other way --

>> categorical(ans)
ans = 
  7×1 categorical array
     08 
     12 
     15 
     76 
     03 
     99 
     00 
>> 

but if you want a straight, ordinary double array to appear that way at the command line, just not possible.

[Sim]

Thanks a lot! I would like to accept both of your answers!!!