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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:

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?Code (Text):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

Thanks

Michael

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# Bizarre result of the sum() function in MATLAB

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