How to find the position of a number in an array?

2.600 visualizaciones (últimos 30 días)
Arnab Pal
Arnab Pal el 15 de Feb. de 2018
Editada: MathWorks Support Team el 14 de Nov. de 2024 a las 6:28
If I have a vector, a = [7 8 8 2 5 6], how do I compute the positions of the value 8? I expect 2 and 3 or (1,2) and (1,3).

Respuesta aceptada

Walter Roberson
Walter Roberson el 14 de Nov. de 2024 a las 0:00
Editada: MathWorks Support Team el 14 de Nov. de 2024 a las 6:28
You can use the “find” function to return the positions corresponding to an array element value. For example: a = [7 8 8 2 5 6]; linearIndices = find(a==8) linearIndices = 2 3 To get the row and column indices separately, use: [row,col] = find(a==8) row = 1 1 col = 2 3 If you only need the position of one occurrence, you could use the syntax “find(a==8,1)”. You can also specify a direction if you specifically want the first or last occurrence, such as “find(a==8,1,’first’). For more information on these options, see “find”.
  2 comentarios
Arvind Andrew Das
Arvind Andrew Das el 19 de Jul. de 2022
i did the find function, but it gives me the ans vector with all of the values of the array and the results are in true or false for my condition( 0 & 1 ).
Walter Roberson
Walter Roberson el 20 de Jul. de 2022
find() can never return 0. Perhaps you are looking at ans for a different operation?

Iniciar sesión para comentar.

Más respuestas (4)

Bhagyesh Shiyani
Bhagyesh Shiyani el 5 de Dic. de 2019
what if i want both 8 positions, any code?
  2 comentarios
Florian Reinbold
Florian Reinbold el 15 de En. de 2020
Hi Bhagyesh
i would suggest this one:
[val, idx] = find(a==8);
It seems to make a great job! :)
Cheers
Florian
Walter Roberson
Walter Roberson el 15 de En. de 2020
This will not return value and index, it will return row and column numbers.

Iniciar sesión para comentar.


Sorne Duong
Sorne Duong el 21 de Jul. de 2021
a = 1, 3, 6, 9, 10, 15
We know the fourth value is 9, but how to find the fourth value in MATLAB?
  4 comentarios
Torsten
Torsten el 30 de Mayo de 2022
Try
values = T_03(int_t_03,4)
Reem RA
Reem RA el 30 de Mayo de 2022
Thanks it worked!!!!

Iniciar sesión para comentar.


Nilesh Kumar Bibhuti
Nilesh Kumar Bibhuti el 15 de Oct. de 2021
Editada: Walter Roberson el 15 de Oct. de 2021
BRO , THIS WILL GIVE U THE DESIRED OUTPUT . HAPPY CODING :)
#include <stdio.h>
#define MAX_SIZE 100 // Maximum array size
int main()
{
int arr[MAX_SIZE] ,brr[MAX_SIZE] ;
int size, i, toSearch, found ,k=0;
/* Input size of array */
printf("Enter size of array: ");
scanf("%d", &size);
/* Input elements of array */
printf("Enter elements in array: ");
for (i = 0; i < size; i++)
{
scanf("%d", &arr[i]);
}
printf("\nEnter element to search: ");
scanf("%d", &toSearch);
for (i = 0; i < size; i++)
{
if (arr[i] == toSearch)
{
brr[k] = i+1 ;
printf("%d ",brr[k]);
k++ ;
}
}
return 0;
}
  1 comentario
Walter Roberson
Walter Roberson el 15 de Oct. de 2021
In C, int size should really be size_t size and your scanf() should be using %lu instead of %d . i and k should also be size_t
You should be checking the return status of each scanf() call .
Also
int main()
should be
int main(void)
unless you are using K&R C from before C was standardized.
The user is expecting the positions to be returned, rather than displayed.
You probably shouldn't be assuming integer for the array, but that would be an acceptable limitation if specifically documented.
You do not use or initialize found.

Iniciar sesión para comentar.


Korosh Agha Mohammad Ghasemi
Korosh Agha Mohammad Ghasemi el 25 de Jun. de 2024
Movida: Voss el 25 de Jun. de 2024
To find the positions of the value 8 in the vector a = [7 8 8 2 5 6], you can use the find function in MATLAB. Here's how you can do it:
a = [7 8 8 2 5 6];
% Find the positions of the value 8
positions = find(a == 8);
disp('Positions of value 8:');
disp(positions);
This code will output the indices of the elements in a that are equal to 8. For the given vector, it will display 2 and 3.
If you need the positions in a 1-based index format like (1,2) and (1,3) (assuming a is a row vector), you can directly use the indices obtained from the find function since MATLAB indexing starts from 1.
Here's the complete example:
a = [7 8 8 2 5 6];
% Find the positions of the value 8
positions = find(a == 8);
% Display the positions in (row, column) format
for i = 1:length(positions)
fprintf('(1,%d)\n', positions(i));
end
This script will output:
(1,2)
(1,3)
This clearly indicates the positions of the value 8 in the vector a.

Categorías

Más información sobre Loops and Conditional Statements en Help Center y File Exchange.

Etiquetas

Aún no se han introducido etiquetas.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by