how to sum floating point elements of an array

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

[Andrei Bobrov]

a = rand(8,1) % the initial array
out = sum(a)

[Yoheena Kotikawatte]

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?

Answer 1

[Jan]

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.

[Oleg Komarov]

Haven't thought of that, but it makes very much sense now.

[Subrat kumar sahoo]

Thanks Jan. thats precisely was my mistake, I already had a variable in the name "sum." Thanks for the help

[Karttikeya Mangalam]

Thanks! Still saving an hour in 2016 :)

[Anu MAngla]

Thanks Jan Simon.. I was unable to find my mistake from a month and i haven't thought of this. Thanks for the help

[Khushi Bhatti]

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]

Saved me too! Thank you!! Glad came across this solution!

Answer 2

[Oleg Komarov]

"??? 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...

[Subrat kumar sahoo]

Thanks Oleg for explaining the error