Pad a character array with n zeros

I know there are formatting tools to pad a certain number of zeros to a number when printing it -- I may be able to use that in some way. But my situation is this: I have binary strings encoded as character arrays: '101010101', etc. I need to have the bit strings to be of a certain length. For example, if that length was 10, '101' would need seven zeros padded on the front: '0000000101', and '111111111' would need one zero padded on the front: '0111111111'.

Is there a quick way where I can have that number of zeros needed (10-numel(num)) padded on the front?

PS - I love the de2bi function where you can specify the number of bits but I am creating really long bit strings and that function only works for numbers less than 2^53-1.

Answer 1

[Walter Roberson]

>> sprintf('%010s', '101')
ans =
0000000101

This is a little obscure but works just fine.

Alternately,

S = '101';
[repmat('0', 1, 10 - length(S)], S]

[Michael]

Thanks Walter -- Is there a way to do the first one with a variable instead of hard coding ten? I see I can do that on the second version...

[Sean de Wolski]

@Michael:

n = 15;

x = '101'

sprintf(sprintf('%%0%is',n),x)

[Walter Roberson]

n = 15;

x = '101';

sprintf('%0*s', n, x)

[Sean de Wolski]

Learn something new every day (hour).

Answer 2

[Sean de Wolski]

To pad a single string:

sprintf('%010s','11');

To pad a cell array of string:

C = {'010';'1';'0111';'01010101'};
D = cellfun(@(x)sprintf('%010s',x),C,'uni',false);