Interweave two arrays in a specific pattern

Asked by Adam Fitchett on 30 Oct 2019

Latest activity Commented on by Daniel M on 30 Oct 2019

5 views (last 30 days)

I have two column vectors each of which is 160 rows long. I want to interweave them such that the first 16 rows of vector 2 are underneath the first 16 rows of vector 1, the second 16 rows of vector 2 are underneath the original second 16 rows of vector 1 and so on. E.g. the vectors are interweaved in alternating blocks of 16. Is there a simple way to do this?

0 Comments

Products

MATLAB

Release

R2017b

2 Answers

Link

Answer by Fangjun Jiang on 30 Oct 2019

Edited by Fangjun Jiang on 30 Oct 2019

%%
a=(1:32)';
b=(10:10:320)';
%%
c=reshape([a,b],16,[]);
d=c(:,[1:2:end,2:2:end]);
e=d(:)
%% better solution from Guillaume
c=[reshape(a,16,[]);reshape(b,16,[])];
e=c(:)

2 Comments

Guillaume on 30 Oct 2019

May be simpler:

reshape([reshape(a, 16, []); reshape(b, 16, [])], [], 1)  %reshape a and b separately into columns of 16 rows. Vertically concatenate the two and reshape back into vector

Fangjun Jiang on 30 Oct 2019

Apparently, it is better! Thanks!

Link

Answer by Daniel M on 30 Oct 2019

Edited by Daniel M on 30 Oct 2019

x = [1:160]';
y = x;
xx = reshape(x,16,[])';
yy = reshape(y,16,[])';
zz = [xx,yy]';
z = zz(:);

2 Comments

Guillaume on 30 Oct 2019

None of the (conjugate!) tranpose are necessary. Simply use zz = [xx; yy]

Daniel M on 30 Oct 2019

details....details...

% edited:
% your starting point, x and y are two column vectors
x = [1:160]';
y = x
%
xx = reshape(x,16,[]); % put into matrix of 16 rows, N columns
yy = reshape(y,16,[]);
zz = [xx,yy]; % vertically concatenate
z = zz(:); % column vector again

Note: the two answers are now identical.

Products

MATLAB

Release

R2017b

You are now following this question

Adam Fitchett (view profile)