# how to sum floating point elements of an array

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Subrat kumar sahoo am 11 Sep. 2012
Kommentiert: SWATI BHARGAVA am 2 Dez. 2019
Hi I have an array which has floating point inputs. I need to sum all the elements to get a single value. The command 'sum' takes only integer inputs and throws error "??? Subscript indices must either be real positive integers or logicals" for double type inputs. Will appreciate any help.
Thanks, Subrat
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Yoheena Kotikawatte am 24 Mär. 2018
Hi! How do i make this work:
k = 25;
v=[1;0];
pvalues=[0:.01:1];
for i1=1:length(pvalues) p=pvalues(i1); A =[(2-p) (0.25*p); p (1.25-0.25*p)]; numbbacteria=(A^k)*v; y(p) = sum(numbbacteria); end
plot(pvalues,y) ylabel('Total number of bacteria'); xlabel('Probability that a bacteria will switch states');
because I get the eror: Subscript indices must either be real positive integers or logicals.
Error in p_file (line 8) y(p) = sum(numbbacteria);
I do understand the eror but how do i make it work with decimals?

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### Akzeptierte Antwort

Jan am 11 Sep. 2012
Bearbeitet: Jan am 11 Sep. 2012
While the command sum accepts arrays of floating point types also (see the documention!), this will fail if you overwrite the name "sum" by a variable:
clear sum % The initial status
sum(rand(1,5)) % works!
sum = 1:10; % Brrr, don't do it, although it is not a bug
sum(rand(1,5)) % Bug!
Check overwritten names by the command whos.
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SWATI BHARGAVA am 2 Dez. 2019
Saved me too! Thank you!! Glad came across this solution!

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### Weitere Antworten (1)

Oleg Komarov am 11 Sep. 2012
"??? Subscript indices must either be real positive integers or logicals"
It means you're doing something:
a = 1:0.1:2;
b = rand(20,1);
b(a)
You cannot select position 1.1, 1.2... of an array (or -1). The indexing of an array is done with whole positive integers 1, 2, 3...
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Subrat kumar sahoo am 11 Sep. 2012
Thanks Oleg for explaining the error

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