How do I convert a numerical vector into a comma-delimited string?
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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
采纳的回答
更多回答（6 个）
Michael
2018-6-15
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.
here's another answer, but is a one liner
strjoin(arrayfun(@(x) num2str(x),n,'UniformOutput',false),',')
Jan Siegmund
2020-6-30
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.
(Quite) A simple approach that has not been mentioned yet -
n = [12345 6789 10234 3452];
out = strjoin(string(n),",")
3 个评论
It is also the fastest -
%Testing with larger values
n = randi([1e3 1e4],[1 100]);
tic;
s1 = sprintf('%.0f,' , n);
s1 = s1(1:end-1);
t(1)=toc;
tic;
s2 = strjoin(arrayfun(@(x) num2str(x),n,'UniformOutput',false),',');
t(2)=toc;
tic;
s3 = regexprep(num2str(n),'\s+',',');
t(3)=toc;
tic;
s4 = strjoin(cellstr(num2str(n')),',');
t(4)=toc;
tic;
s5 = strjoin(string(n),',');
t(5)=toc;
t
isequal(s1,s2,s3,s5)
s4 gives a different output, something with space and all (I'll elaborate tomorrow, it's 3 am here rn)
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
2023-8-19
Even after the change, Method 6 is (marginally) slower than Method 5 (which is the fastest).
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())
Gianfranco Di Domenico
2023-8-18
编辑：Gianfranco Di Domenico
2023-8-18
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 个评论
Interesting.
It looks fine when displayed on screen but the internal string has 2 extra chararters of code 44 ',' and 8 backspash at the end. Not sure what side effect it has when precessing later.
n = [12345 6789]
n_str = sprintf("%s\b", sprintf("%i,", n))
double(char(n_str))
Gianfranco Di Domenico
2023-8-18
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.
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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