MATLAB: How to change the field width of an exponential notation

fprint

Hi, Im trying to change the field width and the number of digits of the exponential, I will like to looks like enginnering notation:
3.45866636216603e+002
and what I get its:
3.45866636216603e+02
The formatSpec have the next form: 
%21.14e
So, I dont know what Im doing wrong, its suppose to the total numbers before e its 21, 14 of them are located after the point. But doesnt seem to be like that.

Best Answer

Given >=2 digits, ensure >=3 digits:
>> val = 3.45866636216603e2;
>> str = sprintf('%.14e',val)
str =
3.45866636216603e+02
>> str = regexprep(sprintf('%.14e',val),'(?<=\D)\d\d$','0$&')
str =
3.45866636216603e+020
Given >=1 digits, ensure >=3 digits:
>> str = regexprep(sprintf('%.14e',val),{'(?<=\D)\d$','(?<=\D)\d\d$'},'0$&')
str =
3.45866636216603e+020
A general solution that can provide any number of digits:
>> num = 3; % required number of digits
>> fun = @(s)sprintf('%0*u',num,sscanf(s,'%u'));
>> str = regexprep(sprintf('%.14e',val),'\d+$','${fun($&)}')
str =
3.45866636216603e+020
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