matrix Questions
3
I am learning about 3d graphics and have stumbled upon matrixes, which I don't fully understand. I have a 3d object, with topology, points in coordinate system and ECS (4x4 matrix of the object).
E...
5
Solved
I have a single vector of flow data (29 data) and a 3D matrix data(360*180*29)
i want to find the correlation between single vector and 3D vector. The correlation matrix will have a size of 360*18...
Barthol asked 3/2, 2012 at 6:59
7
Solved
So the obvious way to transpose a matrix is to use :
for( int i = 0; i < n; i++ )
for( int j = 0; j < n; j++ )
destination[j+i*n] = source[i+j*n];
but I want something that will take ...
12
Solved
I have a matrix (relatively big) that I need to transpose. For example assume that my matrix is
a b c d e f
g h i j k l
m n o p q r
I want the result be as follows:
a g m
b h n
c I o
d j p
e k...
1
Solved
Consider the following code in Python, where multiplying a pre-transposed matrix yields faster execution time compared to multiplying a non-transposed matrix:
import numpy as np
import time
# Gene...
5
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In this question it is explained how to access the lower and upper triagular parts of a given matrix, say:
m = np.matrix([[11, 12, 13],
[21, 22, 23],
[31, 32, 33]])
Here I need to transform th...
7
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When should one use a data.frame, and when is it better to use a matrix?
Both keep data in a rectangular format, so sometimes it's unclear.
Are there any general rules of thumb for when to use wh...
6
Solved
I have a tsv that looks like this (long-form):
one two value
a b 30
a c 40
a d 20
b c 10
b d 05
c d 30
I'm trying to get this into a dataframe for R (or pandas)
a b c d
a 00 30 40 20
b...
3
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I'd like to know if there is a more efficient/pythonic way to add multiple numpy arrays (2D) rather than:
def sum_multiple_arrays(list_of_arrays):
a = np.zeros(shape=list_of_arrays[0].shape) #init...
Exciter asked 9/2, 2021 at 1:18
2
Solved
I am starting to test Haskell for linear algebra. Does anyone have any recommendations for the best package for this purpose? Any other good resources for doing basic matrix manipulation with Haske...
Experientialism asked 26/2, 2010 at 16:58
4
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I am running 64 bit R 3.1 in a 64bit Ubuntu environment with 400GB of RAM, and I am encountering a strange limitation when dealing with large matrices.
I have a numeric matrix called A, that is 4...
6
I have a symbolic array that can be expressed as:
from sympy import lambdify, Matrix
g_sympy = Matrix([[ x, 2*x, 3*x, 4*x, 5*x, 6*x, 7*x, 8*x, 9*x, 10*x],
[x**2, x**3, x**4, x**5, x**6, x**7, x*...
Hispaniola asked 12/6, 2013 at 16:10
17
Solved
I have a list of lists, something like
[[1, 2, 3,],[4, 5, 6,],[7, 8, 9]].
Represented graphically as:
1 2 3
4 5 6
7 8 9
I'm looking for an elegant approach to check the value of neighbours o...
3
I have two large sets of vectors, A and B. Each element of A is a 1-dimensional vector of length 400, with float values between -10 and 10. For each vector in A, I'm trying to calculate the cosine ...
Foresheet asked 3/12, 2015 at 15:48
7
I have the following matrix in Excel:
3 Columns: A, B, C
Row 1: a b c
Row 2: d e f
Row 3: ghi
What I need is a single column with all these values. The result should look like that:
a
b
c
...
4
Supose we have a matrix like this one:
# Set seed
set.seed(12345)
# Generate data.frame
df <- matrix(sample(1:100,100), nrow = 10)
I would like to get the row and column where the first n hi...
3
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I have a vector say
a = c(1,2,3,4,5,6)
I would like to organize them into the elements into an upper triangle matrix (without considering diagonal elements, they are all zero) by row. My goal i...
3
Solved
A question was already asked on how keeping colnames in a matrix when applying apply, sapply, etc. here.
But I didn't find how to keep the column AND row names of a matrix.
Below an example:
mat ...
7
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I have a matrix with 5 columns and 4 rows. I also have a vector with 3 columns. I want to subtract the values in the vector from columns 3,4 and 5 respectively at each row of the matrix.
b <- m...
10
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Is there a built in way of printing a readable matrix in Ruby?
For example
require 'matrix'
m1 = Matrix[[1,2], [3,4]]
print m1
and have it show
=> 1 2
3 4
in the REPL instead of:
=> ...
3
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I'm trying to deduct the 2D-transformation parameters from the result.
Given is a large number of samples in an unknown X-Y-coordinate system as well as their respective counterparts in WGS84 (lon...
Nu asked 18/6, 2013 at 14:24
16
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Say you want to convert a matrix to a list, where each element of the list contains one column. list() or as.list() obviously won't work, and until now I use a hack using the behaviour of tapply :
...
14
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I'm doing a function that multiplies 2 matrices.
The matrices will always have the same number of rows and columns. (2x2, 5x5, 23x23, ...)
When I print it, it doesn't work. Why?
For example, if I c...
Gamete asked 29/11, 2014 at 17:36
7
Solved
I want to create a circulant matrix from a vector in R. A circulant matrix is a matrix with the following form.
1 2 3 4
4 1 2 3
3 4 1 2
2 3 4 1
The second row is the same as the first row except...
Selsyn asked 3/4, 2013 at 18:37
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