How to replace leading zeroes by spaces with regexprep

Question

Blue 2020-7-8

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https://ww2.mathworks.cn/matlabcentral/answers/561902-how-to-replace-leading-zeroes-by-spaces-with-regexprep

评论： madhan ravi 2020-7-9

Hi,

I have a basic question. I simply need to replace the leading zeroes by empty spaces in table T except for the last zero which needs to remain zero. The desired output is output. I know I should probably use regexprep but the exact synthax always throws me off. Its for exportation purposes.

a = {'1231', '0002', '0103', '0000'}';
b = {'000', '000', '000', '000'}';
c = {'0', '0', '0', '0'}';
T = table(a,b,c);
d = {'1231', '   2', ' 103', '   0'}';
e = {'  0', '  0', '  0', '  0'}';
f = {'0', '0', '0', '0'}';
output = table(d,e,f);

Thank you,

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Answer 1

Stephen23 2020-7-9

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https://ww2.mathworks.cn/matlabcentral/answers/561902-how-to-replace-leading-zeroes-by-spaces-with-regexprep#answer_463514

编辑：Stephen23 2020-7-9

在 MATLAB Online 中打开

>> fun = @(c)regexprep(c,'^0+(?=\d)','${char(double($&)-16)}');
>> out = varfun(fun,T)
out = 
    Fun_a     Fun_b    Fun_c
    ______    _____    _____
    '1231'    '  0'    '0'  
    '   2'    '  0'    '0'  
    ' 103'    '  0'    '0'  
    '   0'    '  0'    '0' 

Or

>> fun = @(c)regexprep(c,'^0+(?=\d)','${repmat('' '',1,numel($&))}');
>> out = varfun(fun,T)
out = 
    Fun_a     Fun_b    Fun_c
    ______    _____    _____
    '1231'    '  0'    '0'  
    '   2'    '  0'    '0'  
    ' 103'    '  0'    '0'  
    '   0'    '  0'    '0'

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Stephen23 2020-7-9

编辑：Stephen23 2020-7-9

@madhan ravi: thank you.

"Stephen it would be really great if you could make a separate thread just for regular expression. Like the other threads you made, no pressures indeed!"

So far I have only written the "dynamic variable names tutorial", which mostly consisted of collecting together hundreds of links to related discussions and adding an introduction. Time consuming certainly, but not particularly difficult.

Your suggestion is interesting. How should the tutorial be arranged? What topics need to be covered or explained that are not already covered in the documentation? Perhaps there is already an online tutorial which describes regular expressions similar to MATLAB's, it might be easier to just link to that (if we could identifiy a well-written tutorial).

madhan ravi 2020-7-9

”How should the tutorial be arranged? What topics need to be covered or explained that are not already covered in the documentation?”

To be honest I don’t know how it could be arranged Stephen. But it could cover for example lots of examples which are not covered in the documentation. I will add up some additional ideas in your new thread as well because at the moment the things I learnt about Regex have slightly faded away.

“Perhaps there is already an online tutorial which describes regular expressions similar to MATLAB's, it might be easier to just link to that (if we could identifiy a well-written tutorial).“

There might be many but it wouldn’t match like you describe the concepts!

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Answer 2

James Tursa 2020-7-8

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https://ww2.mathworks.cn/matlabcentral/answers/561902-how-to-replace-leading-zeroes-by-spaces-with-regexprep#answer_463088

编辑：James Tursa 2020-7-8

在 MATLAB Online 中打开

One way:

fun = @(x)sprintf(['%' num2str(numel(x)) 'd'],str2double(x));
d = cellfun(fun,a,'uni',false);
e = cellfun(fun,b,'uni',false);
f = cellfun(fun,c,'uni',false);

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Blue 2020-7-9

Hi. Thank you for your input but this is going to be quite slow. Thats also why I dont want to convert everything to double and then use the pad function.

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Answer 3

Raj Kumar Bhagat 2020-7-9

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https://ww2.mathworks.cn/matlabcentral/answers/561902-how-to-replace-leading-zeroes-by-spaces-with-regexprep#answer_463268

编辑：Raj Kumar Bhagat 2020-7-9

在 MATLAB Online 中打开

I tried using the basic loop statements. I was able to get the required output. Check if this code helps.

if true

p = eliminatePreleadingzeros(a);
function output = eliminatePreleadingzeros(a)
  for i = 1: length(a)
      tempoutput = [];
        for j =1: length(char(a(i)))
            tempchar = char(a(i))
            if ~strcmp(tempchar(j),'0')
                for k = j:length(tempchar)
                    tempoutput = [tempoutput, tempchar(k)];
                end
                break;
            end
        end
        if isempty(tempoutput)
            output(i)={'0'};
        else
            output(i) = {tempoutput};
        end
    end
    output = output';
end
end