replace elements in an Array with other elements

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Rica
Rica el 20 de Jul. de 2015
Comentada: Juan Jiménez el 22 de Jun. de 2020
hi all,
i have the folwing situation:
i have an array:
A=[1 2 3 4 4 4 5 8 7 4 6 4]
i want to find the element equal to the value 4.
I do this:
index=find(A==4)
i want now to replace the element with this index with the previous value. it means i want to get:
A_new=[1 2 3 3 3 3 5 8 7 7 6 6].
i did it with a loop. is there any method without loop?
thank you

Respuesta aceptada

Guillaume
Guillaume el 20 de Jul. de 2015
While it may be possible to do it without a loop, with a combination of diff, find and possibly cumsum it's going to be a lot more obscure than a simple loop and probably not any more efficient.
The simplest loop would be:
for idx = find(A == 4)
A(idx) = A(idx-1);
end
which also works for consecutive elements to replace.

Más respuestas (3)

Walter Roberson
Walter Roberson el 20 de Jul. de 2015
A_new = A;
A_new(index) = A(index-1);
This will fail if the very first thing was a 4, as there is no "previous" for the first element.
  1 comentario
Guillaume
Guillaume el 20 de Jul. de 2015
This also fails on the example given, when there are consecutive elements to replace.

Iniciar sesión para comentar.


Sean de Wolski
Sean de Wolski el 20 de Jul. de 2015
Editada: Sean de Wolski el 20 de Jul. de 2015
A=[1 2 3 4 4 4 5 8 7 4 6 4]
idx = find(A~=4);
B = interp1(idx,A(idx),1:numel(A),'previous','extrap')
Gotta love the 'previous' and 'next' options added to interp1 a few releases ago!

Shashank
Shashank el 14 de Jun. de 2018
How can I copy paste 2nd element to 3rd, 3rd to 4th and so on.. A=[1,2,3,4,5,6,7]; A_New=[1,2,2,3,3,4,4,5,5,6,6,7]; ---> Required

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