Hi Janos, Everton, and Adrien, Thank you very much for your suggestions especially Adrien's explanations are very helpful. I only look from the implement perspective (\=, *=, -= , and += operators are the same) and do not pay attention to the mathematical meaning of the expression.
Best, Hung On Tue, Mar 17, 2020 at 10:53 PM Adrien Escande <[email protected]> wrote: > Hello, > > this is not working, because you are trying to subtract two elements that > are different in nature: a vector and a scalar. From a mathematical point > of view, it doesn't make sense. > By doing v -=2 I assume you are trying to subtract 2 from every component > of v. Some software like matlab offer a *shorcut* in the form v - 2, but > Eigen doesn't (at least not directly). > There are at least two ways to achieve what you want: > * v -= Vector3d::Constant(2), that is you express in a proper > mathematical way what you want > * going into array world as Janos suggested: v.array() -= 2; > > Note that v *= 2 works because it is mathematically valid to multiply a > vector or matrix by a scalar. > > Best regards, > Adrien Escande > > On Wed, Mar 18, 2020 at 10:04 AM Everton Rufino Constantino1 < > [email protected]> wrote: > >> Looking at VectorwiseOp.h there is an -= operator implemented... >> What kind of error are you seeing exactly? >> >> Everton Constantino >> Software Developer >> Application Libraries Optimisation >> Linux Technology Center, IBM Systems >> e-mail: [email protected] >> >> >> >> >> ----- Original message ----- >> From: Janos Meny <[email protected]> >> To: [email protected] >> Cc: >> Subject: [EXTERNAL] Re: [eigen] Vector's -= operator does not seem to work >> Date: Tue, Mar 17, 2020 21:56 >> >> How about using v.array() -= 2; ? >> >> On Wed 18. Mar 2020 at 01:53, Hung Dang <[email protected]> wrote: >> >> Hi, >> >> I try some Eigen examples (see below) and the -= operator is not >> supported. Is there any way to make it work without creating a constant >> vector? >> >> Thank a lot, >> >> Hung >> >> Matrix2d a; >> a << 1, 2, 3, 4; >> Vector3d v(1, 2, 3); >> std::cout << "a * 2.5 =\n" << a * 2.5 << std::endl; >> std::cout << "0.1 * v =\n" << 0.1 * v << std::endl; >> std::cout << "Doing v *= 2;" << std::endl; >> >> v *= 2; >> std::cout << "Now v =\n" << v << std::endl; >> >> // Does not work >> // v -= 2; >> // std::cout << "Now v =\n" << v << std::endl; >> >> >> >> >> >> >> >>
