Shift array to left or right, keep length and feel zero empty area

Hello,

I have an array:

A  = [1 2 3 4 5 6 7 8 9];

I want create B array from A

B = [0 0 1 2 3 4 5 6 7];
or
B = [3 4 5 6 7 8 9 0 0];

How it is possible?

circshift dont feel zeros

Answer 1

[Cris LaPierre]

I'm not aware of a function that will do exactly what you describe. However, the final result is still possible if you are willing to break the process up into steps.

A  = [1 2 3 4 5 6 7 8 9];
B = zeros(size(A));
B(3:end) = A(1:7)

B = 1×9

0 0 1 2 3 4 5 6 7

% or
n = -2;
B = circshift(A,n);
if n>0
    B(1:n) = 0
else
    B(end+n+1:end) = 0
end

B = 1×9

3 4 5 6 7 8 9 0 0

●

[Nik Rocky]

Beautiful! Thank you so much!

[Stephen23]

Note that the IF..ELSE..END can be replaced with one line:

A = 1:9;
n = -2;
B = circshift(A,n);
B([1:n,end+n+1:end]) = 0

B = 1×9

3 4 5 6 7 8 9 0 0

n = +2;
B = circshift(A,n);
B([1:n,end+n+1:end]) = 0

B = 1×9

0 0 1 2 3 4 5 6 7

Answer 2

[Aamod]

Same code for a 2D matrix - shift by shift values and zero pad the extra area.

function Eout = circshiftzeropad(Ein,shifty,shiftx)

%function Eout = circshiftzeropad(Ein,shifty,shiftx)

%shifts and zeropads an array

Eout = circshift(Ein,[shifty shiftx]);

if shiftx <0

Eout(:,(end+shiftx):end)= 0;

else

Eout(:,(1:shiftx))= 0;

end

if shifty <0

Eout((end+shifty):end,:)= 0;

else

Eout((1:shifty),:)= 0;

end

[Enzo]

Thanks a lot, it helped me !

[Aamod]

Wonderful!

Answer 3

[Steven Lord]

If you're using release R2023b or later you could use paddata.

A  = [1 2 3 4 5 6 7 8 9];
B = paddata(A(1:end-2), numel(A), Side="leading")

B = 1×9

0 0 1 2 3 4 5 6 7

C = paddata(A(3:end), numel(A)) % Default is Side="trailing"

C = 1×9

3 4 5 6 7 8 9 0 0

If you object to the fact that I hard-coded "1:end-2" and "3:end":

n = 2;
B = paddata(A(1:(end-n)), numel(A), Side="leading")

B = 1×9

0 0 1 2 3 4 5 6 7

C = paddata(A((1+n):end), numel(A))

C = 1×9

3 4 5 6 7 8 9 0 0