Clear Filters
Clear Filters

To find a vector subset of a matrix in sequence?

3 views (last 30 days)
I have a vector A = [1 2 3] And another matrix B = [2 3 4 1; 1 2 3 4; 2 4 1 3; 2 3 1 4]
I want to know which row of vector A is subset of Matrix B (in same sequence of A, i.e. 1 2 3
The answer is 2nd row of B matrix

Accepted Answer

Thibaut Jacqmin
Thibaut Jacqmin on 27 Jan 2017
Here is a solution in one line :
A = [1 2 3];
B = [2 3 4 1; 1 2 3 4; 2 4 1 3; 2 3 1 4];
% Reshape B in a 1D array (all rows in a line)
C = reshape(B', [1, numel(B)]);
% Then use strfind to find a pattern in a string pattern within a string
linear_index = strfind(C, A);
% Compute the row number of the pattern knowing the initial number of columns
row_number = ceil(linear_index/size(B, 2));
% Or do it in a single line :
row_number = ceil(strfind(reshape(B', [1, numel(B)]), A)/size(B, 2));
  2 Comments
Jan
Jan on 27 Jan 2017
A good idea.
The current version fails, if the searched vector appears over the margins:
B = [2 3 4 1; 2 3 1 4]
But you can filter all occurrences, which do not start between 1 and size(B,2)-length(A).

Sign in to comment.

More Answers (0)

Categories

Find more on Characters and Strings in Help Center and File Exchange

Tags

Community Treasure Hunt

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

Start Hunting!