I have a 25by3 matrix and i want to remove randomly 10 rows (I have already completed this part). The problem is that i want the original matrix which is 25by3 to be 15by3 after removing 10 rows. Thats my question
6 次查看(过去 30 天)
显示 更早的评论
Thats my code
X=[x1 x2 x3]; %25by3 matrix
%
k = randperm(size(X,1));
Ex_Ran= X(k(1:10),:)%extract 10 rows randomly
0 个评论
采纳的回答
Star Strider
2015-5-17
Try this:
X=[x1 x2 x3]; %25by3 matrix
k = randperm(size(X,1));
Ex_Ran = X;
Ex_Ran(k(1:10),:) = [] %extract 10 rows randomly
7 个评论
stelios loizidis
2019-8-6
Hello,
I want to tell you that I have the following issue: I am trying to remove 2000 random columns from a matrix A (1653X8000). I applied the above code but Matlab gives me the following error:
Index exceeds the number of array elements (1653)
The code I wrote:
A=[x1 x2, x3.....] %1653by8000 matrix
k=randperm(size(A,1));
B=A;
B(:,k(1:2000))=[];
Your help is valuable!!
Steven Lord
2019-8-6
k is a reordering of the numbers between 1 and the number of rows in A.
You want a reordering of the numbers between 1 and the number of columns in A (which is the size of A in the second dimension) if you want to use it as a set of indices into the columns of B (which starts off as a copy of A.)
更多回答(3 个)
Mark Stone
2015-5-18
编辑:Mark Stone
2015-5-18
I show you this just so that you 'll be aware of the very handy setdiff function. it might not be as fast executing as the previous answer, but it is elegant.
X =[x1 x2 x3]; %25by3 matrix
k = randperm(size(X,1));
X = X(setdiff(1:25,k(1:10)),:);
Or you can make the left hand side a new variable, such as Y, if you want to preserve the original 25 by 3 matrix as is.
Y = X(setdiff(1:25,k(1:10)),:);
0 个评论
Murali Krishna
2015-5-18
编辑:Murali Krishna
2015-5-18
To extract 10 rows of a given matrix
a=rand(25,3);%25*3 matrix
b=randperm(10);
c=a([b],:);
k=setdiff(a,c,'rows');
2 个评论
Walter Roberson
2015-5-18
That is going to extract the first 10 rows, but in a random order. You need to randperm() over the whole 25 and take only 10 of the scrambled values as the indices to extract.
另请参阅
类别
在 Help Center 和 File Exchange 中查找有关 Characters and Strings 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!