How do I convert a numerical vector into a comma-delimited string?
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D.W. Frye
el 10 de En. de 2011
Comentada: Dyuman Joshi
el 19 de Ag. de 2023
Given a numerical vector, how do I convert it into a comma-delimited string?
For example, if
n = [12345 6789 10234 3452]
convert n to
12345,6789,10234,3452
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Respuesta aceptada
Más respuestas (6)
Michael
el 15 de Jun. de 2018
Have another one-liner:
regexprep(num2str(n),'\s+',',')
If uninitiated in the secrets of (Matlab's) regular expressions: \s stands for any whitespace and the + means 1 or more times. This is needed because the amount of space between the numbers output by num2str varies depending on the length of those numbers.
0 comentarios
Jan Siegmund
el 30 de Jun. de 2020
Here is another oneliner:
strjoin(cellstr(num2str(n')),',')
Testing all four types with a script
n = randi(100,[1 100]);
tic;
s1 = sprintf('%.0f,' , n);
s1 = s1(1:end-1);
toc
tic;
s2 = strjoin(arrayfun(@(x) num2str(x),n,'UniformOutput',false),',');
toc
tic;
s3 = regexprep(num2str(n),'\s+',',');
toc
tic;
s4 = strjoin(cellstr(num2str(n')),',');
toc
deliveres:
Elapsed time is 0.000248 seconds.
Elapsed time is 0.005549 seconds.
Elapsed time is 0.000746 seconds.
Elapsed time is 0.003352 seconds.
The accepted answer is the fastest.
0 comentarios
Dyuman Joshi
el 18 de Ag. de 2023
(Quite) A simple approach that has not been mentioned yet -
n = [12345 6789 10234 3452];
out = strjoin(string(n),",")
3 comentarios
Bruno Luong
el 18 de Ag. de 2023
Editada: Bruno Luong
el 18 de Ag. de 2023
The first method is not optimal with format '%.0f', for integer better using '%i' (method 6)
n = randi([1e3 1e4],[1 1000]);
t = zeros(1,6);
t(1) = timeit(@() csnum1(n), 1);
t(2) = timeit(@() csnum2(n), 1);
t(3) = timeit(@() csnum3(n), 1);
t(4) = timeit(@() csnum4(n), 1);
t(5) = timeit(@() csnum5(n), 1);
t(6) = timeit(@() csnum6(n), 1);
tms = t*1e3
function s1 = csnum1(n)
s1 = sprintf('%.0f,' , n);
s1 = s1(1:end-1);
end
function s2 = csnum2(n)
s2 = strjoin(arrayfun(@(x) num2str(x),n,'UniformOutput',false),',');
end
function s3 = csnum3(n)
s3 = regexprep(num2str(n),'\s+',',');
end
function s4 = csnum4(n)
s4 = strjoin(cellstr(num2str(n')),',');
end
function s5 = csnum5(n)
s5 = strjoin(string(n),',');
end
function s = csnum6(n)
s = sprintf('%i,' , n);
s = s(1:end-1);
end
Dyuman Joshi
el 19 de Ag. de 2023
Even after the change, Method 6 is (marginally) slower than Method 5 (which is the fastest).
RST
el 3 de Ag. de 2023
We can also use compose() for a formatted one-liner:
a = rand(5,1);
csva = strjoin(compose('%.3f', a), ', ')
and also for 2D arrays:
b = rand(3,4);
csvb = strjoin(join(compose( '%.3f', b), ', '), newline())
0 comentarios
Gianfranco Di Domenico
el 18 de Ag. de 2023
Editada: Gianfranco Di Domenico
el 18 de Ag. de 2023
EDIT: The backspace character is handled differently according to the final "usage" of the string. For instance, it works perfectly when displaying the string in the terminal; however, printing the string to a file does not remove the comma. Moreover, the byte array corresponding to the string retains both the comma and the backspace character.
More elegant, one liner:
n = [12345 6789 10234 3452]
n_str = sprintf("%s\b", sprintf("%i,", n))
The logic:
- The nested sprintf creates a string of comma-separated values, but has a trailing comma
- The top-level sprintf prints the generated strings and the \b character (backspace) removes the trailing comma
3 comentarios
Gianfranco Di Domenico
el 18 de Ag. de 2023
I just noticed this behavior.
I will edit the original answer because it seems that the behavior depends on the final usage of the string. For instance, fprintf-ing to a file does NOT work! The comma is retained.
Bruno Luong
el 18 de Ag. de 2023
Editada: Bruno Luong
el 18 de Ag. de 2023
Example
n = [12345 6789 10234 3452]
n_str = sprintf("%s\b", sprintf("%i,", n))
str2num(n_str) % oh oh ...
str2num(extractBefore(n_str,strlength(n_str)-1))
This might create some frustration and pain of debugging
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