n-dimensional | 易学教程

How to make Numpy treat each row/tensor as a value

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问题 Many functions like in1d and setdiff1d are designed for 1-d array. One workaround to apply these methods on N-dimensional arrays is to make numpy to treat each row (something more high dimensional) as a value. One approach I found to do so is in this answer Get intersecting rows across two 2D numpy arrays by Joe Kington. The following code is taken from this answer. The task Joe Kington faced was to detect common rows in two arrays A and B while trying to use in1d . import numpy as np A = np

How to make Numpy treat each row/tensor as a value

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C++ 2D vector and operations

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问题 How can one create a 2D vector in C++ and find its length and coordinates ? In this case, how are the vector elements filled with values? Thanks. 回答1: If your goal is to do matrix computations, use Boost::uBLAS. This library has many linear algebra functions and will probably be a lot faster than anything you build by hand. If you are a masochist and want to stick with std::vector , you'll need to do something like the following: std::vector<std::vector<double> > matrix; matrix.resize(10);

Java - How to build unique object tuples (n-dimension)?

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问题 I have the following challenge that I need to create unique object tuples out of object lists. The speical challenge is here how I can do it for dynamic list sizes (n-dimension)? It is easy in case you have a fixed dimension. I hope somebody knows a third party API or has some hints for me how I can reach this. The exampel below shows it for a 3 lists, so it is easier to explain. I have the objects sorted by its class in a list e.g. lista = {a1,a2} listb = {b1,b2,b3} listc = {c1,c2} I like to

C++ How to generate the set of cartesian product of n-dimensional tuples

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问题 I wish to generate some data that represents the co-ordinates of a cloud of points representing an n-cube of n dimensions. These points should be evenly distributed throughout the n-space and should be able to be generated with a user-defined spacing between them. This data will be stored in an array. 回答1: I have found an implementation of a cartesian product using Boost.MPL. There is an actual Cartesian product in Boost as well but that is a preprocessor directive, I assume it is of no use

Dimensions of fractals: boxing count, hausdorff, packing in R^n space

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问题 I would like to calculate dimensions of fractal written as a n-dimensional array of 0s and 1s. It includes boxing count, hausdorff and packing dimension. I have only idea how to code boxing count dimensions (just counting 1's in n-dimensional matrix and then use this formula: boxing_count=-log(v)/log(n); where n-number of 1's and n-space dimension (R^n) This approach simulate counting minimal resolution boxes 1 x 1 x ... x 1 so numerical it is like limit eps->0 . What do you think about this

n-dimensional matching algorithm

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问题 Looking for some advice here. Does anyone know a good place to start looking into matching algorithm in a n-dimensional space. For example, any dating site out there must be using some sort of algorithm to match 2 people. What I have read is that we can map characteristics of a person in a n-dimensional array with a point system for each characteristic. Once we have all (available) characteristics of a person, we can represent this person in a point within a n-dimensional array. Then, to

Dimensions of fractals: boxing count, hausdorff, packing in R^n space

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I would like to calculate dimensions of fractal written as a n-dimensional array of 0s and 1s. It includes boxing count, hausdorff and packing dimension. I have only idea how to code boxing count dimensions (just counting 1's in n-dimensional matrix and then use this formula: boxing_count=-log(v)/log(n); where n-number of 1's and n-space dimension (R^n) This approach simulate counting minimal resolution boxes 1 x 1 x ... x 1 so numerical it is like limit eps->0 . What do you think about this solution? Do you have any idea (or maybe code) for calculating hausdorff or packing dimension? The

C++ 2D vector and operations

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How can one create a 2D vector in C++ and find its length and coordinates ? In this case, how are the vector elements filled with values? Thanks. If your goal is to do matrix computations, use Boost::uBLAS . This library has many linear algebra functions and will probably be a lot faster than anything you build by hand. If you are a masochist and want to stick with std::vector , you'll need to do something like the following: std::vector<std::vector<double> > matrix; matrix.resize(10); matrix[0].resize(20); // etc You have a number of options. The simplest is a primitive 2-dimensional array:

How do I get the two last dimensions of an N-D array as a 2D array?

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I have a 3D array in MATLAB, with size(myArray) = [100 100 50] . Now, I'd like to get a specific layer, specified by an index in the first dimension, in the form of a 2D matrix. I tried myMatrix = myArray(myIndex,:,:); , but that gives me a 3D array with size(myMatrix) = [1 100 50] . How do I tell MATLAB that I'm not interested in the first dimension (since there's only one layer), so it can simplify the matrix? Note: I will need to do this with the second index also, rendering size(myMatrix) = [100 1 50] instead of the desired [100 50] . A solution should be applicable to both cases, and