CODEWITHSUNDEEP
matlabvectorvectorizationscalar
MGA
MGA

Reputation: 1668

Non-element-wise vector division in Matlab returns a scalar! What is it?

I spent over an hour chasing a bug in my code which was leading to a precision error. It turned out that in one of my equations, I had forgotten to divide two vectors element-wise; I had written / instead of ./. Usually Matlab gives an error in these cases, e.g. if you try to multiply two vectors with * instead of .*. But in this case it's happily returning a scalar value! Is this supposed to happen, and does this value have any meaning?

For example,

x = 0 : 0.01 : 1;
y = x/exp(x);

sets y=0.3132.

Upvotes: 2

Views: 135

Answers (1)

gnovice
gnovice

Reputation: 125874

Yes, this is supposed to happen. You used the matrix right division operator /, and in this particular case it found a scalar value of y that solved the following system of equations in a least-squares sense:

y*exp(x) = x;

Upvotes: 2

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