# Numerics

**URL:** https://discourse.julialang.org/c/domain/numerics/20.md?page=29

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**Page:** 30

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## [Any way to auto-reformat Binary without extra tail "000s..."](https://discourse.julialang.org/t/any-way-to-auto-reformat-binary-without-extra-tail-000s/49944)

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**Author:** [@teriiju](https://discourse.julialang.org/u/teriiju)\
**Replies:** 1\
**Last updated:** [November 10, 2020, 8:44pm UTC](https://discourse.julialang.org/t/any-way-to-auto-reformat-binary-without-extra-tail-000s/49944 "2020-11-10T20:44:02Z")

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Hi, using the Dec to Bin convertion, I’ve pickup this lines of codes which seem to do the job : dek = 21 string(bswap(dek), base = 2) "1010100000........." Now, in this way I’m getting a very long format : Out\[9\]: “1…

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## [Proper Julia syntax for Kriging interpolation with Geostats.jl?](https://discourse.julialang.org/t/proper-julia-syntax-for-kriging-interpolation-with-geostats-jl/49506)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 8\
**Last updated:** [November 6, 2020, 2:13am UTC](https://discourse.julialang.org/t/proper-julia-syntax-for-kriging-interpolation-with-geostats-jl/49506 "2020-11-06T02:13:42Z")

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Hi, I’m trying to use Kriging to interpolate between data values in a discrete array. The following code (and variations of it) give errors like, MethodError: no method matching EstimationProblem(::Set{Float64}, ::Regul…

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## [Faces & Vertices of N Linear Constraints](https://discourse.julialang.org/t/faces-vertices-of-n-linear-constraints/49347)

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**Author:** [@anon92994695](https://discourse.julialang.org/u/anon92994695)\
**Replies:** 15\
**Last updated:** [November 3, 2020, 11:07pm UTC](https://discourse.julialang.org/t/faces-vertices-of-n-linear-constraints/49347 "2020-11-03T23:07:29Z")

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Here’s a fun one, so instead of doing what I normally do(hacking away at code), I figured I’d ask if people had tools to recommend for solving a problem. I know you people working in optimization and geometry live in thi…

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## [Convert a float into a string](https://discourse.julialang.org/t/convert-a-float-into-a-string/49513)

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**Author:** [@teriiju](https://discourse.julialang.org/u/teriiju)\
**Replies:** 25\
**Last updated:** [November 3, 2020, 10:26pm UTC](https://discourse.julialang.org/t/convert-a-float-into-a-string/49513 "2020-11-03T22:26:00Z")

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Hi, Is it possible to convert a float number into a string ? i.e. 32.234565 ()number into “32.234565” (string) or this works only with integers ? Thanks

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## [Divrem maximum precision for the remain](https://discourse.julialang.org/t/divrem-maximum-precision-for-the-remain/49510)

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**Author:** [@teriiju](https://discourse.julialang.org/u/teriiju)\
**Replies:** 14\
**Last updated:** [November 3, 2020, 7:30pm UTC](https://discourse.julialang.org/t/divrem-maximum-precision-for-the-remain/49510 "2020-11-03T19:30:14Z")

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Hi, Can divrem return a remainder with a higher digit precision ? more digits after the dot… or is it just meant to round the remainder to 2 digits most always… Thanks

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## [Eigvals() results being slightly different when Distributed.jl are used](https://discourse.julialang.org/t/eigvals-results-being-slightly-different-when-distributed-jl-are-used/49516)

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**Author:** [@zhaiyusci](https://discourse.julialang.org/u/zhaiyusci)\
**Replies:** 2\
**Last updated:** [November 3, 2020, 4:51pm UTC](https://discourse.julialang.org/t/eigvals-results-being-slightly-different-when-distributed-jl-are-used/49516 "2020-11-03T16:51:30Z")

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Hi friends, recently I am working on some eigen problems in quantum physics. I need to construct and diagonalize quite a few symmetric real matrices so I am using Distributed, the standard library. See a minimal example…

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## [How to find location of Minimum in Interpolation function?](https://discourse.julialang.org/t/how-to-find-location-of-minimum-in-interpolation-function/48528)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 11\
**Last updated:** [November 3, 2020, 2:50am UTC](https://discourse.julialang.org/t/how-to-find-location-of-minimum-in-interpolation-function/48528 "2020-11-03T02:50:09Z")

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Hi, when using an Interpolation object to approximate a function with values known over a few dozen discrete data points, how can I find where the (local) minimum of the function is? (Assuming that the minimum is not act…

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## [Setting ApproxFun Space , tried several tricks but still receive \*\*ERROR: LoadError: Cannot infer spaces\*\* – specifically when using GeneralizedGenerated.jl for Generalized generated functions](https://discourse.julialang.org/t/setting-approxfun-space-tried-several-tricks-but-still-receive-error-loaderror-cannot-infer-spaces-specifically-when-using-generalizedgenerated-jl-for-generalized-generated-functions/48909)

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**Author:** [@Marc.Cox](https://discourse.julialang.org/u/Marc.Cox)\
**Replies:** 21\
**Last updated:** [October 26, 2020, 7:15pm UTC](https://discourse.julialang.org/t/setting-approxfun-space-tried-several-tricks-but-still-receive-error-loaderror-cannot-infer-spaces-specifically-when-using-generalizedgenerated-jl-for-generalized-generated-functions/48909 "2020-10-26T19:15:20Z")

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Setting ApproxFun Space , tried several tricks but still receive ERROR: LoadError: Cannot infer spaces – specifically when using GeneralizedGenerated.jl for Generalized generated functions # Begin Preamble using Linea…

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## [Is there a way to check Sobol parameters Confidence interval (CI)?](https://discourse.julialang.org/t/is-there-a-way-to-check-sobol-parameters-confidence-interval-ci/26692)

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**Author:** [@alewolf](https://discourse.julialang.org/u/alewolf)\
**Replies:** 7\
**Last updated:** [November 2, 2020, 8:46am UTC](https://discourse.julialang.org/t/is-there-a-way-to-check-sobol-parameters-confidence-interval-ci/26692 "2020-11-02T08:46:04Z")

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Hi, Running sobol\_sensitivity in DiffEqSensitivity gives some negative values - even while useing the equation ind documents. function f(du,u,p,t) du\[1\] = p\[1\]\*u\[1\] - p\[2\]\*u\[1\]\*u\[2\] du\[2\] = -3\*u\[2\] + u\[1\]\*u\[2\] end…

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## [Combining 2 ternary conditions, how to?](https://discourse.julialang.org/t/combining-2-ternary-conditions-how-to/49358)

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**Author:** [@teriiju](https://discourse.julialang.org/u/teriiju)\
**Replies:** 10\
**Last updated:** [October 31, 2020, 8:39am UTC](https://discourse.julialang.org/t/combining-2-ternary-conditions-how-to/49358 "2020-10-31T08:39:37Z")

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Hi, newbie, wonderings :slightly\_smiling\_face: 1: if it is safe to combine 2 (or more) ternary conditions. as in this way : (e\>f) ? “e” : (f\<g) ? “f” : “g” - with : e=2, f=4, g=8 ? or if that is not recomended. …

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## [How do I get the coordinates for the dofs in JuAFEM?](https://discourse.julialang.org/t/how-do-i-get-the-coordinates-for-the-dofs-in-juafem/49229)

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**Author:** [@bcsj](https://discourse.julialang.org/u/bcsj)\
**Replies:** 1\
**Last updated:** [October 29, 2020, 1:26pm UTC](https://discourse.julialang.org/t/how-do-i-get-the-coordinates-for-the-dofs-in-juafem/49229 "2020-10-29T13:26:27Z")

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I have been trying to get a hang on the JuAFEM package and running the Heat Equation example from the documentation I have noticed that the ordering of the resulting vector appears to not correspond to the ordering of no…

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## [COBOL and Julia comparison](https://discourse.julialang.org/t/cobol-and-julia-comparison/49166)

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**Author:** [@bocc](https://discourse.julialang.org/u/bocc)\
**Replies:** 16\
**Last updated:** [October 28, 2020, 6:25pm UTC](https://discourse.julialang.org/t/cobol-and-julia-comparison/49166 "2020-10-28T18:25:46Z")

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Hello, I’d like to state in advance that I have negligible familiarity with number representations, so please excuse any inaccuracies. I also enjoy getting rid of legacy systems. I have recently read an article which p…

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## [Difference-Differential system in ModelingToolkit.jl](https://discourse.julialang.org/t/difference-differential-system-in-modelingtoolkit-jl/48605)

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**Author:** [@Honza9723](https://discourse.julialang.org/u/Honza9723)\
**Replies:** 5\
**Last updated:** [October 26, 2020, 7:34pm UTC](https://discourse.julialang.org/t/difference-differential-system-in-modelingtoolkit-jl/48605 "2020-10-26T19:34:10Z")

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Dear All, I would like to ask for advice regarding ModellingToolkit.jl. I am working on a problem (macroeconomic model) that reduces to the solution of a highly nonlinear dynamic system. Because of high-nonlinearity and…

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## [Techniques to improve resolution of a system of nonlinear equations](https://discourse.julialang.org/t/techniques-to-improve-resolution-of-a-system-of-nonlinear-equations/48712)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 13\
**Last updated:** [October 22, 2020, 10:28am UTC](https://discourse.julialang.org/t/techniques-to-improve-resolution-of-a-system-of-nonlinear-equations/48712 "2020-10-22T10:28:36Z")

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Hello, I would like to solve a set of N = 300 independent 1D nonlinear equations of the type f\_i(x\_i) = a\_i where the a\_i are given and each function f\_i is a univariate strictly increasing bijection. There is a unique…

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## [Help with debugging some code for the MKLSparse package](https://discourse.julialang.org/t/help-with-debugging-some-code-for-the-mklsparse-package/48764)

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**Author:** [@dmbates](https://discourse.julialang.org/u/dmbates)\
**Replies:** 0\
**Last updated:** [October 21, 2020, 5:51pm UTC](https://discourse.julialang.org/t/help-with-debugging-some-code-for-the-mklsparse-package/48764 "2020-10-21T17:51:41Z")

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On the principle that “given enough eyeballs, all bugs are shallow” I am asking for help in debugging a problem in the dmb/matrix\_sparse branch of the MKLSparse package. The purpose of this package is to use Intel’s Mat…

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## [Identify important subspaces of a function without squaring the conditioning number](https://discourse.julialang.org/t/identify-important-subspaces-of-a-function-without-squaring-the-conditioning-number/48664)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 2\
**Last updated:** [October 20, 2020, 4:06am UTC](https://discourse.julialang.org/t/identify-important-subspaces-of-a-function-without-squaring-the-conditioning-number/48664 "2020-10-20T04:06:19Z")

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Hello, I would like to find the important directions in the input and output spaces for a \\mu-measurable function f: \\mathbb{R}^n \\xrightarrow{} \\mathbb{R}^d. One way to identify these directions is to look at the eige…

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## [Most Accurate/Efficient Interpolation approach for 1D/2D, discrete-continuous hybrid problem](https://discourse.julialang.org/t/most-accurate-efficient-interpolation-approach-for-1d-2d-discrete-continuous-hybrid-problem/48515)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 4\
**Last updated:** [October 18, 2020, 7:14pm UTC](https://discourse.julialang.org/t/most-accurate-efficient-interpolation-approach-for-1d-2d-discrete-continuous-hybrid-problem/48515 "2020-10-18T19:14:13Z")

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Hi all, looking for advice on the best way to get very accurate results in finite computing time, for this problem: A discrete grid in x, with f(x) values at each point. For any initial choice of x0, need to interpolate…

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## [NLsolve Intermediate Value Theorem](https://discourse.julialang.org/t/nlsolve-intermediate-value-theorem/48509)

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**Author:** [@brett\_knoss](https://discourse.julialang.org/u/brett_knoss)\
**Replies:** 1\
**Last updated:** [October 16, 2020, 6:58pm UTC](https://discourse.julialang.org/t/nlsolve-intermediate-value-theorem/48509 "2020-10-16T18:58:33Z")

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Does NLsolve use the Intermediate Value Theorem, how do I aproxemetly solve a problem like 1000=(x)^2+10sin(x) I know that f(a)=f(0)=0 and that f(b) can be f(100)=(100)^2+10sin(100)\>=9990 how would I find x such that…

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## [How to start Partial Differential Equation (PDE) Solving in Julia for modified Wave Equation](https://discourse.julialang.org/t/how-to-start-partial-differential-equation-pde-solving-in-julia-for-modified-wave-equation/46555)

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**Author:** [@CosmoProf](https://discourse.julialang.org/u/CosmoProf)\
**Replies:** 50\
**Last updated:** [October 12, 2020, 11:40pm UTC](https://discourse.julialang.org/t/how-to-start-partial-differential-equation-pde-solving-in-julia-for-modified-wave-equation/46555 "2020-10-12T23:40:05Z")

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Hi, after working with ordinary differential equations so far, I now have to numerically solve a partial differential equation (PDE) in Julia, and I’m not sure where to start. My equation is like the usual wave equation…

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## [How to tackle 2D Poisson equation?](https://discourse.julialang.org/t/how-to-tackle-2d-poisson-equation/48185)

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**Author:** [@sw72](https://discourse.julialang.org/u/sw72)\
**Replies:** 3\
**Last updated:** [October 12, 2020, 11:27am UTC](https://discourse.julialang.org/t/how-to-tackle-2d-poisson-equation/48185 "2020-10-12T11:27:08Z")

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Can anyone point me in the right direction for solving a 2D Poisson equation in a circular region? I’m a little overwhelmed by the number of different Julia packages which a google search returns, and it can be hard to …

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## [Partial SVD](https://discourse.julialang.org/t/partial-svd/47820)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 7\
**Last updated:** [October 6, 2020, 6:57am UTC](https://discourse.julialang.org/t/partial-svd/47820 "2020-10-06T06:57:27Z")

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Hello, Is there a command to only perform a partial SVD decomposition of a non-square matrix?

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## [Numerical Continuation in Julia?](https://discourse.julialang.org/t/numerical-continuation-in-julia/5522)

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**Author:** [@s-marashi](https://discourse.julialang.org/u/s-marashi)\
**Replies:** 9\
**Last updated:** [October 4, 2020, 12:49pm UTC](https://discourse.julialang.org/t/numerical-continuation-in-julia/5522 "2020-10-04T12:49:44Z")

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What are available options for numerical continuation in Julia? While it’s irrelated does any body know about Auto software?

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## [State of JuAFEM](https://discourse.julialang.org/t/state-of-juafem/39183)

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**Author:** [@CorbinFoucart](https://discourse.julialang.org/u/CorbinFoucart)\
**Replies:** 2\
**Last updated:** [October 2, 2020, 6:17pm UTC](https://discourse.julialang.org/t/state-of-juafem/39183 "2020-10-02T18:17:09Z")

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I’m reading the JuAFEM dev docs and it’s not immediately apparent whether a few things are supported. Are: general unstructured grids (tet, hex) wedge elements nonconforming and adaptive meshes supported? Secondly, i…

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## [Complex-valued functions with real arguments - ForwardDiff, JuliaDiff](https://discourse.julialang.org/t/complex-valued-functions-with-real-arguments-forwarddiff-juliadiff/27386)

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**Author:** [@marcvb97](https://discourse.julialang.org/u/marcvb97)\
**Replies:** 6\
**Last updated:** [September 28, 2020, 10:41pm UTC](https://discourse.julialang.org/t/complex-valued-functions-with-real-arguments-forwarddiff-juliadiff/27386 "2020-09-28T22:41:30Z")

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When executing the following code to apply ForwardDiff to a complex-valued function with real argument: using ForwardDiff f2(t::Real) = real( (cos(t) + 1im\*sin(t))^(1/2) ) t = pi/2 ForwardDiff.derivative(f2,t) I get th…

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## [Finite Difference, calculating the differentiation matrix, etc](https://discourse.julialang.org/t/finite-difference-calculating-the-differentiation-matrix-etc/47180)

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**Author:** [@natgeo-wong](https://discourse.julialang.org/u/natgeo-wong)\
**Replies:** 6\
**Last updated:** [September 25, 2020, 4:01pm UTC](https://discourse.julialang.org/t/finite-difference-calculating-the-differentiation-matrix-etc/47180 "2020-09-25T16:01:43Z")

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Hello, I have been trying to solve vorticity and streamfunctions using finite-difference methods using linear algebra. However, when I calculate the streamfunction \\psi using the formula \\zeta = \\nabla^2\\psi I get ext…

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## [Sparse high dimensional array support einsum?](https://discourse.julialang.org/t/sparse-high-dimensional-array-support-einsum/47222)

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**Author:** [@yupbank](https://discourse.julialang.org/u/yupbank)\
**Replies:** 6\
**Last updated:** [September 24, 2020, 9:51pm UTC](https://discourse.julialang.org/t/sparse-high-dimensional-array-support-einsum/47222 "2020-09-24T21:51:30Z")

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Hello there, I’m wondering if there is any effort in high dimensional sparse tensors with einsum support? For example, I’m working on something that can be abstracted into high dimensional tensors and i need to perform…

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## [Lazy representation of x^T A x](https://discourse.julialang.org/t/lazy-representation-of-x-t-a-x/47087)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 6\
**Last updated:** [September 22, 2020, 8:36pm UTC](https://discourse.julialang.org/t/lazy-representation-of-x-t-a-x/47087 "2020-09-22T20:36:21Z")

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Hello, I have a complicated code (nested calls to subroutines) that computes an expression of the form x^T A x, where A is not necessarily PSD. Is it possible to construct a lazy representation of A, in the same spirit …

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## [Hierarchical quadtree for fast mutipole method](https://discourse.julialang.org/t/hierarchical-quadtree-for-fast-mutipole-method/46350)

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**Author:** [@mleprovost](https://discourse.julialang.org/u/mleprovost)\
**Replies:** 3\
**Last updated:** [September 11, 2020, 3:43pm UTC](https://discourse.julialang.org/t/hierarchical-quadtree-for-fast-mutipole-method/46350 "2020-09-11T15:43:41Z")

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Hello, Is there a package that constructs a hierarchical quadtree given a set of non-uniform points in 2D? I would like to play around with fast multipole methods.

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## [ODE where u and du are different sizes](https://discourse.julialang.org/t/ode-where-u-and-du-are-different-sizes/46213)

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**Author:** [@klowrey](https://discourse.julialang.org/u/klowrey)\
**Replies:** 11\
**Last updated:** [September 8, 2020, 1:30am UTC](https://discourse.julialang.org/t/ode-where-u-and-du-are-different-sizes/46213 "2020-09-08T01:30:03Z")

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I didn’t see an obvious solution in the docs so I thought I would ask: I have an ODE problem where the state is a different size than the change in state. Specifically, lets say my state of \[pos; vel\] includes a quatern…

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## [Error: Problems with using VectorOfArray() with DifferentialEquations package](https://discourse.julialang.org/t/error-problems-with-using-vectorofarray-with-differentialequations-package/46049)

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**Author:** [@MJMAG](https://discourse.julialang.org/u/MJMAG)\
**Replies:** 4\
**Last updated:** [September 5, 2020, 11:13am UTC](https://discourse.julialang.org/t/error-problems-with-using-vectorofarray-with-differentialequations-package/46049 "2020-09-05T11:13:32Z")

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Hey there, I am new to the community. I don’t have too much experience with the DifferentialEquations package. I am trying to model Lotka Volterra dynamics with two guilds and in these guilds various species. For this…

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