Clear Filters
Clear Filters

Add first element to a cell array

138 views (last 30 days)
Luis Isaac
Luis Isaac on 18 Dec 2015
Commented: Josh on 4 May 2024
I would like to add a new element in the first position in an cell array For example if ArrCell={[1],[2],[3],[4],[5]} is the existing cell and [new] is a matrix. I would like to get ArrCell={[new],[1],[2],[3],[4],[5]}
Of course, I can get this result using a temporal cell array and looping over all the elements of the existing one, but the quesion is if there an efficient way to get this result
Thanks in advance,

Accepted Answer

Adam on 18 Dec 2015
ArrCell = [ { new }, ArrCell ];
should work. I'm not at my machine with Matlab at the moment so can't double-check, but fairly sure that works.
Adam on 20 Mar 2020
ArrCell was a row array. You can't concatenate vertically a scalar and a 5-element row array.
Image Analyst
Image Analyst on 20 Mar 2020
new = magic(3) % A matrix
ArrCell={[1],[2],[3],[4],[5]} % A cell array
ArrCell = [ { new }, ArrCell ] % Adam uses comma
ArrCell2 = [ { new }; ArrCell ]; % Daniel uses semicolon
new =
8 1 6
3 5 7
4 9 2
ArrCell =
1×5 cell array
{[1]} {[2]} {[3]} {[4]} {[5]}
ArrCell =
1×6 cell array
{3×3 double} {[1]} {[2]} {[3]} {[4]} {[5]}
Error using vertcat
Dimensions of arrays being concatenated are not consistent.
Error in test1 (line 12)
ArrCell2 = [ { new }; ArrCell ];

Sign in to comment.

More Answers (2)

Image Analyst
Image Analyst on 18 Dec 2015
But the big question is why are you even using a cell array for that instead of a simple numerical array. Cell arrays are complicated and use a huge amount of overhead. From what you've shown there is no reason to use one. I recommend this instead
Arr = [1,2,3,4,5];
Arr = [new, 1,2,3,4,5]
Luis Isaac
Luis Isaac on 18 Dec 2015
I using a cell array because ArrCell is composed of vectors and matrices of different sizes, i.e. size of [new] is different, or could be different, than [1]
Josh on 4 May 2024
appreciate this nudge in a more efficient direction, i fallback on cells arrays out of habit and ease but switching over to numerical arrays where possible...i make animations and cells help when image sizes are changing at least but seem uneccessary when image size is fixed

Sign in to comment.

Fletcher Garrison
Fletcher Garrison on 3 Feb 2021
Edited: Fletcher Garrison on 3 Feb 2021
You can also use:
Arrcell = {1,2,3,4,5};
new = magic(5);
Arrcell = horzcat(new,Arrcell);


Community Treasure Hunt

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

Start Hunting!