Delete row from Matrix
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I have a Matrix of 400 rows and 40 columns. I want to completely remove rows 3 and 9 to get a matrix with 398 rows. How can I do it in MATLAB.
3 个评论
Yuvraj Praveen Soni
2019-12-9
if assume A is your matrix with 400 rows and 40 column,
To remove 3rd row
a(3,:)=[];
now your 9th row become 8th row;
a(8,:)=[];
and with this your 3rd and 9th row will be deleted, you can also check the size by
size(a);
Thank You
Gokul Krishna N
2020-11-2
Thanks
采纳的回答
Jan
2012-6-22
编辑：MathWorks Support Team
2018-11-9
If you have a matrix A and want to delete the 3rd and 9th rows, you can use the command:
A([3,9],:) = [];
5 个评论
Srikanth
2018-8-9
Does this use the same technique as a row deletion in a database. Because if we say we delete more than 1000 entries recursively, then should we be worried about any [primary keys.
Walter Roberson
2018-9-6
databases have their own implementations and their own tradeoffs. For example,
deletes = [3, 9];
q = ['(', strjoin(sprintfc('%d', deletes), ','), ')'];
sqlquery = ['DELETE * FROM inventoryTable WHERE productNumber in ' q];
curs = exec(conn,sqlquery);
How the database implements this is up to the database. As is typical with databases, the efficiency of this can depend upon whether productNumber is an indexed key. But that has nothing to do with MATLAB.
Katarina
2019-6-18
I used this in MATLAB R2017a and e.g.
A(3,:) = []
removes a row, but
A([3,5],:) = []
A([3,3],:) = []
A([k,k],:) = []
also removes only a row, but not a column as said above.
Is it that it doesn't work in my version of matlab of this answer needs updating?
Walter Roberson
2019-6-18
Katarina, I am not clear as to where you are seeing anything about deleting columns in this Answer?
If you want to delete a column then name it in the second index:
A(:,k) = [];
Arezoo Samiei
2021-10-7
Thank you so much Jan!
更多回答（5 个）
Peter
2012-11-30
32 个投票
"I have a Matrix of 400 rows and 40 columns.I want to completely remove rows 3 and 9 to get a matrix with 398 rows. How can I do it in MATLAB."
Matrix_2 = Matrix_1( [1:2,4:8,10:end] , : )
Best,
Pete
Dan W
2015-1-23
I'm not sure if this is new syntax or not, but it works with R2012a and it's fast and simple.
x = rand(100);
tic;
x([3,9],:) = [];
toc; % Elapsed time is 0.000230 seconds.
3 个评论
Mehul Agrawal
2016-6-10
Thanks, this works pretty easy. But I have a problem where the elements to remove are decided dynamically. So, I have a matrix m1 of size 100 X 100. And another matrix m2 of size 10X1. m2 has the row number to remove from m1 (they are not in any order). What is the best way to do this ?
Eg: m1 = rand(100); m2 = [1,6,4,8,10]; (this is the output of another function call).
Andrei Bobrov
2016-6-10
Hi Mehul! It new question.
Andrei Bobrov
2016-6-10
out = m1;
out(m2,:) = [];
Andrei Bobrov
2012-6-21
m = m(setdiff(1:size(m,1),[3,9]),:);
5 个评论
Sean de Wolski
2012-6-21
mmm glass half full
Ryan
2012-6-21
Anyone care to explain this one?
Walter Roberson
2012-6-21
It copies the rows of m that are _not_ row 3 or 9.
Jan
2012-6-22
SETDIFF has a remarkable overhead. ISMEMBER is smarter and twice as fast for a 100x100 matrix:
m = m(~ismember(1:size(m, 1), [3,9]), :);
pradeep kumar
2014-8-30
@ Andrei Bobrov , @ Walter Roberson,@ Jan Simson . how delete a particular row and column of a matrix by using "setdiff" . Say m= [1 2 3 4 ; 5 6 7 8; 9 10 11 12 ; 13 14 15 16 ]. i want to delete 1st row and 2nd column to obtain m=[5 7 8; 9 11 12;13 15 16]
Alireza Rezvani
2016-6-19
5 个投票
sry, how i can Deleting individual columns of a matrix, any body know?
2 个评论
Muhammad Usman Saleem
2016-6-19
Assume out is your matrix and you want to delete its first column, try this code,
out(:,1) = [];
surendra bala
2018-3-31
Yes. This is the easiest way you can do.
LISSA DUVVU
2018-9-29
1 个投票
i want to delete all columns data where the 4th row contains number 7
1 个评论
Jan
2018-10-7
Please do not attach a new (and very vague) question in the section for answers of another questions. Such thread-hijacking is confusing only, because it is not longer clear, to which question an answer belong. Please open your own question and delete this pseudo-answer. Thanks.
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