complex-numbers

问题 According to the boost documentation, the boost special functions bessel function (specifically the modified bessel function) should be able to accept a complex input. However, when I attempt to feed it one, I get a compile error complaining that there is no < operator for operand types float and std::complex<float> . Here is my code: using namespace boost::math; std::complex<float> cpxTerm = std::complex<float>(m_u1 * cos(az), -wbar * cos(sin(lim))); std::complex<float> besselTerm = cyl

问题 This code print *, sqrt(cmplx(-1)) print *, sqrt(cmplx(-1,0)) print *, sqrt((-1,0)) print *, sqrt(-(1,0)) gives me this output (0.00000000,1.00000000) (0.00000000,1.00000000) (0.00000000,1.00000000) (0.00000000,-1.00000000) I believe that the correct algebra is sqrt(-1)=i . Why the result of the last line? The compiler version is GCC 7.3.0, running on Linux openSUSE 42.2 (x86_64). EDIT Following @francescalus answer I have tried more cases: print *, sqrt((-1,-0)) print *, sqrt((-1,-0.)) print

问题 Take this simple example: a = [1 2i]; x = zeros(1,length(a)); for n=1:length(a) x(n) = isreal(a(n)); end In an attempt to vectorize the code, I tried: y = arrayfun(@isreal,a); But the results are not the same: x = 1 0 y = 0 0 What am I doing wrong? 回答1: This certainly appears to be a bug, but here's a workaround: >> y = arrayfun(@(x) isreal(x(1)),a) ans = 1 0 Why does this work? I'm not totally sure, but it appears that when you perform an indexing operation on the variable before calling

问题 I have a set of data points, which are complex numbers which have, let’s say, 8 rows and 6 columns. If you look at the program, you can see that data sets are arranged very randomly. 1st, 2nd, 3rd columns are okay, but 4th column, is bit anomalous. What I mean to say is that after element at B(5, 4) (i.e. 25.9868674011374) it is coming 2.74257567017122 [B(6, 4)] instead of 26.8410063269595 which has gone to B(6, 6). I want that column arranged in ascending order (every sorting should be done

问题 I am trying to evaluate this integral in matlab matlab is treating 'ans' as a symbol because of 'I'. How to convert this 'I' into 'i' so that ans becomes a complex number. much appreciated! 回答1: The symbolic math toolbox has an overloaded double function that can be used to convert from sym to double representation (if the expression is a symbolic constant or is a constant expression). For example: ans_sym = vpa(1+1*i); ans_double = double(ans_sym); Look here for more information: http://www

问题 This question already has an answer here : R and MATLAB returning different eigenvectors (1 answer) Closed 2 years ago . I want to compute the eigenvalues of a complex matrix in R. Comparing the values obtained in MATLAB, I don't get the same eigenvalues obtained in R computing it from the exact same matrix. In R, I used eigen() . In MATLAB used eig() or eigs() (both functions give out the same eigenvalues but different to the R ones). For real matrices, R and MATLAB are consistent. How to

问题 I try to follow example from that website: http://en.cppreference.com/w/cpp/numeric/complex But I get other results. For example for that code: std::complex<double> z1 = 1i * 1i; // imaginary unit squared std::cout << "i * i = " << z1 << '\n'; It works great, I get in the console: i * i = (-1,0) But other example: std::complex<double> z3 = std::exp(1i * M_PI); // Euler's formula std::cout << "exp(i * pi) = " << z3 << '\n'; I get error: call to 'exp' is ambiguous So I tried that one: double PI

问题 I'm using the <complex> library in C++. Is it possible to access the real and complex parts of a complex number using the [] operator? I want to use myComplexNum[0] instead of myComplexNum.real() and myComplexNum[1] instead of myComplexNum.imag() . I tried to do it using MingW 4.5.2, and I receive the error: no match found for 'operator[]' . I really need to use the [] operator for now, because otherwise I would have to change hundreds of lines of code. 回答1: Nope. You could derive from std:

问题 How do I get an absolute value for a double complex variable? def f(): cdef double complex aaa = 1 + 2j cdef double bbb = abs(aaa) The second assignment is highlighted yellow in cython -a html output: aaa is converted to python object prior to applying abs() . How do I call abs() on c/cpp level? PS I understand that cdef extern from "complex.h": double abs(double complex) would solve it, but I see the following instructions in the generated c/cpp file: #if CYTHON_CCOMPLEX #define __Pyx_c_abs

问题 I am trying to use GSL for complex numbers , complex vectors and complex matrices in my project. I am using VS2010 and I added the address of library in Configuration Properties>C/C++>General>Additional Include Directories . But I have a stupid problem. As far as I understood, I can not use = to assign two gsl_complex , gsl_vector_complex or gsl_matrix_complex to each other. For vectors I have to use gsl_vector_complex_set and for matrices gsl_matrix_complex_set . But for gsl_complex, I only