# How to get the same number of char as number of decimals using num2str?

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Louis Tomczyk am 16 Sep. 2022
Kommentiert: Louis Tomczyk am 17 Sep. 2022
Dear all,
I want to get the decimal part of a number.
I have written this small function:
function dec = get_decimals(input)
str = num2str(input) % convert to string
index = strfind(str,'.'); % locate the comma/point
dec = str2double(str(index+1:end)); % take the end
end
However if my input has too many decimals, the function will truncate my number:
>> dec = get_decimals(3.141592653)
str =
'3.1416'
decimals =
1416
How to solve it?
Best,
louis
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### Akzeptierte Antwort

Bruno Luong am 16 Sep. 2022
input = pi
input = 3.1416
str = num2str(input,16)
str = '3.141592653589793'
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Louis Tomczyk am 16 Sep. 2022
Ok thanks a lot, below a function I suggest:
function dec = get_decimals(varargin)
% ---------------------------------------------
% ----- INFORMATIONS -----
% Function name : GET_DECIMALS
% Author : louis tomczyk
% Institution : Telecom Paris
% Email : louis.tomczyk.work@gmail.com
% Date : 2022-09-16
% Version : 1.0
%
% ----- MAIN IDEA -----
% Return the decimal part of a given input.
%
% ----- INPUTS -----
% VARARGIN{1} the number from which we want the decimals
% VARARGIN{2} the number of decimals wanted [OPTIONAL]
%
% ----- BIBLIOGRAPHY -----
% Functions :
% Author :
% Author contact :
% Date :
% Title of program :
% Code version :
% Type :
% -----------------------
% Articles
% Author :
% Title :
% Jounal :
% Volume - N° :
% Date :
% DOI :
% ---------------------------------------------
input = varargin{1};
% conversion to string
if nargin == 1
str = num2str(input);
else
str = num2str(input,varargin{2});
end
% locating the decimals
index = strfind(str,'.');
% getting the decimals
dec = str2double(str(index+1:end));
% if no decimals
if isnan(dec)
dec = [];
end
end
Best,

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### Weitere Antworten (1)

James Tursa am 16 Sep. 2022
You might look into using the fix( ) function to isolate the fractional part of your number and then work with that directly.
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James Tursa am 16 Sep. 2022
Bearbeitet: James Tursa am 16 Sep. 2022
@Louis Tomczyk As you have just learned, it is best to post your real problem up front so as to avoid answers that don't really help you. In addition to Bruno's latest comment, here are other methods for determining if a finite number is an integer value:
x==fix(x)
x==floor(x)
x==round(x)
Louis Tomczyk am 17 Sep. 2022
I know it, but usually I like to try things my own way, not getting directly answer which will surely be much more efficient.
I like to see the reasoning process suggested by others to get the best of this sharing experience.
Thanks again anyway to both of you.
Best,
louis

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