Questions tagged [multidimensional-array]
Multidimensional-arrays can be described as multi-dimensional tables. Each index used in order to find a given element is called a dimension.
multidimensional-array
35,712
questions
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answers
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views
How do I make a flat list out of a list of lists?
I have a list of lists like
[
[1, 2, 3],
[4, 5, 6],
[7],
[8, 9]
]
How can I flatten it to get [1, 2, 3, 4, 5, 6, 7, 8, 9]?
If your list of lists comes from a nested list ...
- 54.5k
1565
votes
88
answers
1.3m
views
Merge/flatten an array of arrays
I have a JavaScript array like:
[["$6"], ["$12"], ["$25"], ["$25"], ["$18"], ["$22"], ["$10"]]
How would I go about merging the separate inner arrays into one like:
["$6", "$12", "$25", ...]
- 19.1k
1409
votes
17
answers
1.2m
views
How to Sort a Multi-dimensional Array by Value
How can I sort this array by the value of the "order" key?
Even though the values are currently sequential, they will not always be.
Array
(
[0] => Array
(
[...
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1399
votes
56
answers
2.8m
views
How can I create a two dimensional array in JavaScript?
I have been reading online and some places say it isn't possible, some say it is and then give an example and others refute the example, etc.
How do I declare a 2 dimensional array in JavaScript? (...
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votes
30
answers
3.0m
views
How to define a two-dimensional array? [duplicate]
I want to define a two-dimensional array without an initialized length like this:
Matrix = [][]
But this gives an error:
IndexError: list index out of range
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678
votes
23
answers
552k
views
Sort array of objects by one property
How can I sort this array of objects by one of its fields, like name or count?
Array
(
[0] => stdClass Object
(
[ID] => 1
[name] => Mary Jane
[...
- 67.5k
651
votes
32
answers
1.1m
views
How do I count the occurrence of a certain item in an ndarray?
How do I count the number of 0s and 1s in the following array?
y = np.array([0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 0, 1])
y.count(0) gives:
numpy.ndarray object has no attribute count
- 7,215
645
votes
30
answers
1.3m
views
How do I declare a 2d array in C++ using new?
How do i declare a 2d array using new?
Like, for a "normal" array I would:
int* ary = new int[Size]
but
int** ary = new int[sizeY][sizeX]
a) doesn't work/compile and b) doesn't accomplish what:
...
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610
votes
23
answers
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Sort an array of associative arrays by column value
Given this array:
$inventory = array(
array("type"=>"fruit", "price"=>3.50),
array("type"=>"milk", "price"=>2.90),
array("type"=>"pork", "price"=>5.43),
);
I would like ...
- 22.7k
581
votes
18
answers
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views
How do you add an array to another array in Ruby and not end up with a multi-dimensional result?
I tried:
somearray = ["some", "thing"]
anotherarray = ["another", "thing"]
somearray.push(anotherarray.flatten!)
I expected
["some", "thing"...
- 5,843
522
votes
5
answers
762k
views
Multidimensional Array [][] vs [,] [duplicate]
double[][] ServicePoint = new double[10][9]; // <-- gives an error (1)
double[,] ServicePoint = new double[10,9]; // <-- ok (2)
What's their difference? (1) yields an error, what's the reason?
...
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519
votes
13
answers
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views
Differences between a multidimensional array "[,]" and an array of arrays "[][]" in C#?
What are the differences between multidimensional arrays double[,] and array of arrays double[][] in C#?
If there is a difference?
What is the best use for each one?
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515
votes
5
answers
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views
How do I use arrays in C++?
C++ inherited arrays from C where they are used virtually everywhere. C++ provides abstractions that are easier to use and less error-prone (std::vector<T> since C++98 and std::array<T, n> ...
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votes
9
answers
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What is the purpose of meshgrid in NumPy?
What is the purpose of np.meshgrid? I know it creates some kind of grid of coordinates for plotting, but I can't see the direct benefit of it.
The official documentation gives the following example, ...
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477
votes
23
answers
836k
views
PHP multidimensional array search by value
I have an array where I want to search the uid and get the key of the array.
Examples
Assume we have the following 2-dimensional array:
$userdb = array(
array(
'uid' => '100',
...
- 4,809
475
votes
13
answers
1.7m
views
Syntax for creating a two-dimensional array in Java
Consider:
int[][] multD = new int[5][];
multD[0] = new int[10];
Is this how you create a two-dimensional array with 5 rows and 10 columns?
I saw this code online, but the syntax didn't make sense.
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votes
19
answers
1.1m
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Passing a 2D array to a C++ function
I have a function which I want to take, as a parameter, a 2D array of variable size.
So far I have this:
void myFunction(double** myArray){
myArray[x][y] = 5;
etc...
}
And I have ...
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447
votes
3
answers
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views
What is the difference between flatten and ravel functions in numpy?
import numpy as np
y = np.array(((1,2,3),(4,5,6),(7,8,9)))
OUTPUT:
print(y.flatten())
[1 2 3 4 5 6 7 8 9]
print(y.ravel())
[1 2 3 4 5 6 7 8 9]
Both function return the ...
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434
votes
8
answers
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Difference between numpy.array shape (R, 1) and (R,)
In numpy, some of the operations return in shape (R, 1) but some return (R,). This will make matrix multiplication more tedious since explicit reshape is required. For example, given a matrix M, if we ...
- 20.6k
394
votes
31
answers
1.2m
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How to initialize a two-dimensional array (list of lists, if not using NumPy) in Python?
I'm beginning python and I'm trying to use a two-dimensional list, that I initially fill up with the same variable in every place. I came up with this:
def initialize_twodlist(foo):
twod_list = []...
- 5,197
394
votes
5
answers
208k
views
What is the difference between ndarray and array in NumPy?
What is the difference between ndarray and array in NumPy? Where is their implementation in the NumPy source code?
- 4,465
383
votes
5
answers
482k
views
How do I use np.newaxis?
What is numpy.newaxis and when should I use it?
Using it on a 1-D array x produces:
>>> x
array([0, 1, 2, 3])
>>> x[np.newaxis, :]
array([[0, 1, 2, 3]])
>>> x[:, np....
- 4,099
378
votes
31
answers
440k
views
How to Flatten a Multidimensional Array?
Is it possible, in PHP, to flatten a (bi/multi)dimensional array without using recursion or references?
I'm only interested in the values so the keys can be ignored, I'm thinking in the lines of ...
- 154k
367
votes
64
answers
410k
views
How do you rotate a two dimensional array?
Inspired by Raymond Chen's post, say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I'd like to see some real world ...
366
votes
8
answers
179k
views
Understanding NumPy's einsum
How does np.einsum work?
Given arrays A and B, their matrix multiplication followed by transpose is computed using (A @ B).T, or equivalently, using:
np.einsum("ij, jk -> ki", A, B)
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votes
20
answers
1.1m
views
How do you extract a column from a multi-dimensional array?
Does anybody know how to extract a column from a multi-dimensional array in Python?
jaweria
288
votes
24
answers
474k
views
in_array() and multidimensional array
I use in_array() to check whether a value exists in an array like below,
$a = array("Mac", "NT", "Irix", "Linux");
if (in_array("Irix", $a))
{
echo "Got Irix";
}
//print_r($a);
but what about ...
- 56.5k
283
votes
6
answers
281k
views
How do you get the width and height of a multi-dimensional array? [duplicate]
I have an array defined:
int [,] ary;
// ...
int nArea = ary.Length; // x*y or total area
This is all well and good, but I need to know how wide this array is in the x and y dimensions individually. ...
- 21.1k
215
votes
6
answers
332k
views
How to sort an array of objects with jquery or javascript [duplicate]
I have an array of objects:
var array = [(id, name, value),(id, name, value)]; //and so on
How do I get the array to be sorted in ascending order of the atribute name (array[i][1])?
I've tried to ...
- 3,628
211
votes
10
answers
264k
views
Using NumPy to build an array of all combinations of two arrays
I'm trying to run over the parameters space of a six-parameter function to study its numerical behavior before trying to do anything complex with it, so I'm searching for an efficient way to do this.
...
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205
votes
10
answers
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views
How do I Sort a Multidimensional Array in PHP [duplicate]
I have CSV data loaded into a multidimensional array. In this way each "row" is a record and each "column" contains the same type of data. I am using the function below to load my CSV file.
function ...
- 2,466
195
votes
10
answers
599k
views
Convert a 1D array to a 2D array in numpy
I want to convert a 1-dimensional array into a 2-dimensional array by specifying the number of columns in the 2D array. Something that would work like this:
> import numpy as np
> A = np.array([...
- 3,579
186
votes
9
answers
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views
Rotating a two-dimensional array in Python
In a program I'm writing the need to rotate a two-dimensional array came up. Searching for the optimal solution I found this impressive one-liner that does the job:
rotated = zip(*original[::-1])
I'...
- 4,860
173
votes
4
answers
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views
How to access first level keys of a 2d array with a foreach loop? [duplicate]
How do I access the first level key of a two-dimensional array using a foreach loop?
I have a $places array like this:
[Philadelphia] => Array
(
[0] => Array
(...
- 3,480
171
votes
13
answers
788k
views
Getting the array length of a 2D array in Java
I need to get the length of a 2D array for both the row and column. I’ve successfully done this, using the following code:
public class MyClass {
public static void main(String args[])
{
int[...
- 20.1k
167
votes
16
answers
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views
Checking if array is multidimensional or not?
What is the most efficient way to check if an array is a flat array
of primitive values or if it is a multidimensional array?
Is there any way to do this without actually looping through an
array and ...
- 33.1k
165
votes
6
answers
296k
views
How to re-index all subarray elements of a multidimensional array?
The question is how to reset key e.g. for an array:
Array (
[1_Name] => Array (
[1] => leo
[4] => NULL
)
[1_Phone] => Array (
[1] => 12345
...
- 4,407
161
votes
19
answers
179k
views
Matrix Transpose in Python [duplicate]
I am trying to create a matrix transpose function for python but I can't seem to make it work.
Say I have
theArray = [['a','b','c'],['d','e','f'],['g','h','i']]
and I want my function to come up ...
- 9,297
161
votes
6
answers
460k
views
Loop a multidimensional array and only print two specific column values per row
How can I print the filepath and filename values from each row?
Array (
[0] => Array (
[fid] => 14
[list] => 1
[data] => Array (
...
- 17.7k
160
votes
15
answers
557k
views
How to create multidimensional array
Can anyone give me a sample/example of JavaScript with a multidimensional array of inputs? Hope you could help because I'm still new to the JavaScript.
Like when you input 2 rows and 2 columns the ...
- 1,631
153
votes
2
answers
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views
Why is the enumeration value from a multi dimensional array not equal to itself?
Consider:
using System;
public class Test
{
enum State : sbyte { OK = 0, BUG = -1 }
static void Main(string[] args)
{
var s = new State[1, 1];
s[0, 0] = State.BUG;
...
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150
votes
4
answers
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views
Selecting specific rows and columns from NumPy array
I've been going crazy trying to figure out what stupid thing I'm doing wrong here.
I'm using NumPy, and I have specific row indices and specific column indices that I want to select from. Here's the ...
- 2,019
149
votes
18
answers
304k
views
How to sum all column values in multi-dimensional array?
How can I add all the columnar values by associative key? Note that key sets are dynamic.
Input array:
Array
(
[0] => Array
(
[gozhi] => 2
[uzorong] => ...
- 5,097
141
votes
10
answers
296k
views
PHP Multidimensional Array Searching (Find key by specific value)
I have this multidimensional array. I need to search it and return only the key that matches the value of the "slug". I know there are other threads about searching multidimensional arrays, but I'm ...
- 1,413
140
votes
14
answers
76k
views
PHP best way to MD5 multi-dimensional array?
What is the best way to generate an MD5 (or any other hash) of a multi-dimensional array?
I could easily write a loop which would traverse through each level of the array, concatenating each value ...
- 1,879
137
votes
3
answers
83k
views
Argmax of numpy array returning non-flat indices
I'm trying to get the indices of the maximum element in a Numpy array.
This can be done using numpy.argmax. My problem is, that I would like to find the biggest element in the whole array and get the ...
- 28.4k
135
votes
9
answers
161k
views
PHP - Merging two arrays into one array (also Remove Duplicates)
Hi I'm Trying to merge two arrays and also want to remove duplicate values from final Array.
Here is my Array 1:
Array
(
[0] => stdClass Object
(
[ID] => 749
[post_author] =...
- 3,740
127
votes
16
answers
274k
views
How to sort 2 dimensional array by column value?
Can any one help me sort a 2 dimensional Array in JavaScript?
It will have data in the following format:
[12, AAA]
[58, BBB]
[28, CCC]
[18, DDD]
It should look like this when sorted:
[12, AAA]
[18,...
- 12k
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votes
9
answers
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Javascript Map Array Last Item
I have this:
map = ranks.map((row, r) => (
row.map((rank, i) => {
return [element(r, i, state, rank, toggled, onClick)];
})
));
It maps through a 2-dimentional array.
After each row, I'...
- 2,573
123
votes
14
answers
473k
views
The best way to print a Java 2D array? [closed]
I was wondering what the best way of printing a 2D array in Java was?
I was just wondering if this code is good practice or not?
Also any other mistakes I made in this code if you find any.
int rows = ...
- 1,283