# Bizarre result of the sum() function in MATLAB

• MATLAB

## Main Question or Discussion Point

Hello,

Am was trying to figure out why some code was not working and narrowed it down to a little loop that was not being executed.

x is a 4x1 vector with 0 or 1 as each element, eg. x = [0; 0; 1; 1]. The code was required to sum the columns and if this sum was positive (ie. if there were any nonzero elements) it would execute another loop.

The vector was [1; 1; 1; 1] and it was not executing, so I tested the code. Here is copy pasted results of me experimenting and eventually fixing the problem using "clear all" command:

Code:
x =
1
1
1
1
EDU>> sum(x)
ans =
1.4142    1.4142         0         0
EDU>> sum(x')
ans =
1.4142    1.4142         0         0
EDU>> x=[1;1;1;1]
x =
1
1
1
1
EDU>> sum(x)
ans =
1.4142    1.4142    1.4142    1.4142
EDU>> r = [1,2,3]
r =
1     2     3
EDU>> sum(r)
ans =
1.4142    1.4142         0
EDU>> clear all
EDU>> r = [1,2,3]
r =
1     2     3
EDU>> sum(r)
ans =
6
The "clear all" seems to fix everything. But I can't figure out what was wrong. I wasn't doing anything out of the ordinary. Anyone have any ideas what was going wrong?

Thanks
Michael