What does it mean to have a lone plus sign in the exponent/superscript (Modified Weiszfeld algorithm)

functions notation

Solution 1:

I have come across this notation in a different context (page 80, eq. (4.40)), where it was defined as

$$ x^+ \equiv \max(x,0) $$

And correspondingly

$$ x^- \equiv \min(x,0) $$

That is, the $+$ or $-$ indicates that the value is clamped to non-negative or non-positive numbers. Next to the other term in that equation, it seems likely that the same meaning is intended here.

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