how to sum floating point elements of an array

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Subrat kumar sahoo
Subrat kumar sahoo 2012-9-11
评论： SWATI BHARGAVA 2019-12-2
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
  2 个评论
Yoheena Kotikawatte
Yoheena Kotikawatte 2018-3-24
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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采纳的回答

Jan
Jan 2012-9-11
编辑：Jan 2012-9-11
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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Khushi Bhatti
Khushi Bhatti 2019-3-12
Thank you so much Jan! it took me two hours to find my mistake. you just solved it in a second. very helpful
SWATI BHARGAVA
SWATI BHARGAVA 2019-12-2
Saved me too! Thank you!! Glad came across this solution!

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更多回答（1 个）

Oleg Komarov
Oleg Komarov 2012-9-11
"??? 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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