delete element from vector
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Hi everyone
how can I delete element from vector .... for example
a=[1,2,3,4,5]
how can I delete 3 from above vector to be
a=[1,2,4,5]
thank you
majid
7 commentaires
Rosie
le 5 Juil 2017
Modifié(e) : Walter Roberson
le 5 Juil 2017
Hi majed
You can use the follwoing
a(index)=[]
a(3)=[]
the number will delete
Good luck
Hamna Ameer
le 29 Sep 2017
Modifié(e) : Hamna Ameer
le 29 Sep 2017
a(3)=[] how can i directly store this in a new vector say b?
Réponse acceptée
Daniel Shub
le 24 Sep 2012
Modifié(e) : MathWorks Support Team
le 9 Nov 2018
I can think of three ways that are all slightly different
a=[1,2,3,4,5];
If you want to get rid of all cases where a is exactly equal to 3
b = a(a~=3);
If you want to delete the third element
b = a;
b(3) = [];
or on a single line
b = a([1:2, 4:end]);
Or, as Jan suggests:
a = [2,3,1,5,4]
a(a == 3) = []
6 commentaires
Plus de réponses (7)
Jan
le 24 Sep 2012
Modifié(e) : Jan
le 24 Sep 2012
a = [1,2,3,4,5]
a(3) = []
Or:
a = [2,3,1,5,4]
a(a == 3) = []
These methods are explained exhaustively in the "Getting Started" chapters of the documentation. It is strongly recommended to read them completely. The forum is not though to explain the fundamental basics. Thanks.
5 commentaires
Keanu
le 12 Juin 2024
A point of clarification for anyone who may be confused:
Consider the two arrays p = [10;20;30;40] and b = [10,20,30,40] (note the semicolon vs. comma) as an example. In this case, p(3) = [] and b(3) = [] will remove the third element from the array entirely, leaving p = [10;20;40] and b = [10,20,40].
If we were to mistakenly say p(3,1) = [] or b(1,3) = [], MATLAB will throw an error: "A null assignment can have only one non-colon index." Of course, this minor distinction will not be immediately clear to a beginner. Moreover, I do not expect anyone to understand this distinction from reading the "exhaustive" documentation.
The help forums are a guide to anyone with a legitimate question. To this day, I am puzzled by responses that jab at the author for merely asking.
Rik
le 12 Juin 2024
Modifié(e) : Rik
le 12 Juin 2024
I'm surprised that is the error message you get, since it doesn't (at first glance at least) match the cause of the error, and yet:
p = [10;20;30;40];p(3,1) = []
But your comparison is strained, since your code has in indexing error, which is only superficially related to the deletion of array elements.
The only problem with this question is that it should be covered by any half-decent tutorial, perhaps in the first 15 minutes even. In addition to this, you can find extra information in the documentation. My personal bar is that you shouldn't be able to enter the question in Google and get the solution in the first result.
masoud sistaninejad
le 23 Août 2021
A = [ 1 2 3 4 5 6 7]
B = [1 3 6]
C = setdiff(A,B)
2 commentaires
Emma Fickett
le 29 Oct 2022
I've scoured through so many forums trying to remove a vector of values from another vector and setdiff does exactly what I needed, thank you so much!!
Will Reeves
le 15 Fév 2022
really crude, but if you wanted to remove a row defined by and index, rather than a value, you could do something like this:
function out=removeRow(in,index)
% removes a row from an matrix
[~,n]=size(in);
if index>n || index<0
error('index needs to be within the range of the data')
else
if n==1
out=[]; % you've removed the last entry
else
% strip out the required entry
if index==1
out=in(2:end);
elseif index==n
out=in(1:end-1);
else
out=in([1:index-1 index+1:n]);
end
end
end
0 commentaires
Abdul samad
le 4 Août 2023
Modifié(e) : Abdul samad
le 4 Août 2023
Yes , you can delete 3 from the given array by assigning the null matrix, like this .
In the command window do like this.
>> a=[1,2,3,4,5];
>> a(3) = [ ];
>>a
This will delete the 3 from the array a = [1,2,3,4,5];
Thank You
0 commentaires
Sibghat
le 2 Mar 2024
The removal of the element at the 3rd index has already been addressed. However, if you want to remove all occurences of the number '3' from the array 'a', you can use the following code (with and without using the find method).
% For instance, let's modify the array 'a'
a = [1, 3, 2, 3, 4, 3, 5, 3];
b = find(a == 3); % Find the index of the element to delete
% The above line-of-code will also work without using the find keyword...
a(b) = []; % Delete the element(s)
a
1 commentaire
Sibghat
le 2 Mar 2024
And if you want to store the removed values in another variable and display the the exact position of the value. You can do it by either replacing the other values with zeroes or by replacing the desired value with zeroes. Hopefully, the following code will help.
a = [1, 3, 2, 3, 4, 3, 5, 3];
indices_of_3 = find(a == 3); % Find indices of elements equal to 3
removed_values = a(a == 3); % Store the removed values in another variable named 'removed_values'
% Create a vector with zeroes where the number is 3
b = zeros(size(a));
b(a ~= 3) = a(a ~= 3);
% Create a vector with zeroes where the number is not 3
c = zeros(size(a));
c(indices_of_3) = a(indices_of_3);
% Remove all occurrences of 3 from 'original_vector'
a(a == 3) = [];
% Display the results
% Modified vector after removal of all occurrences of 3
a
% Removed values
removed_values
% Displaying zero where values is 3
b
% Displaying zero where value is not 3
c
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