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I want to multiply a matrix by its transposed in order to knwo if it verify QtQ=I.
Yet when I compute it on matlab I get something strange using a concept I'm not aware of: conj(x).
- Therefore, how to multiply a matrix by its transposed?
Here is the code I tried:
>> syms x
>> A=[cos(x) -sin(x);
sin(x) cos(x)]
A =
[ cos(x), -sin(x)]
[ sin(x), cos(x)]
>> A'*A
ans =
[ cos(conj(x))*cos(x) + sin(conj(x))*sin(x), sin(conj(x))*cos(x) - cos(conj(x))*sin(x)]
[ cos(conj(x))*sin(x) - sin(conj(x))*cos(x), cos(conj(x))*cos(x) + sin(conj(x))*sin(x)]
Revolucion for Monica
Posted 2016-06-19T11:32:08.583
Reputation: 167
Have you already looked in matlab help? What remains unclear? – Johannes Tue – 2016-06-19T11:35:26.430
@Alex.S Yes, I did, but to my mind a<sub>1,1</sub> should have been 1 for instance. And instead it gives me the complex conjugate... – Revolucion for Monica – 2016-06-19T11:48:35.867
users of matlab are often scientists, more scientist than programmer, and they may find that a matlab specific support site is more beneficial e.g. http://uk.mathworks.com/matlabcentral/answers/?requestedDomain=www.mathworks.com Also people there are more mathematical and scientific and may be better candidates to answer such a mathematical question. Many left tried going from matlab to python but found what scientist described to me as a "lack of support" and switched to matlab so I guess a matlab forum is better for a scientist than SO(and def better than SU).
– barlop – 2016-06-19T11:57:46.403@barlop okay, too bad :( – Revolucion for Monica – 2016-06-19T12:03:07.063
@Marine1 too good you mean. There is a lot of support for scientists stuck with matlab, less so with python. Where that support is shouldn't matter to you. You shouldn't think negatively if you got an answer that makes sense and points you in the right direction. I can assure you that a bunch of PhD scientists on a matlab forum could solve your matlab problem quicker than they can pick their nose or quicker than they can make small talk. – barlop – 2016-06-19T12:10:01.380
@Marine1 Do you know if
xis real? From your use ofQ(as opposed toU), I am guessing you are talking about orthogonal matrices and soxis real? – edwinksl – 2016-06-26T06:29:02.317@barlop, OK, have to ask (for context): how long do you think it takes a bunch of PhD scientists to pick their nose? And you don't qualify that in your comment, so don't say it depends on how much practice they have. Also, you refer to a bunch of scientists, but just one nose. Are you assuming a number of related scientists with a genetic abnormality, co-joined at the nose, or is the nose a single organ the scientists are growing in the lab. Nose-picking time could be assumed to be different if the nose isn't attached to their face. Inquiring minds want to know. :-) – fixer1234 – 2016-10-03T18:25:51.407