# Addition to specified elements in a vector with for loop to create a new vector

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Ali Tawfik am 8 Nov. 2019
Kommentiert: Ali Tawfik am 9 Nov. 2019
Hi all,
I am trying to add to specified elements in a vector to create a new one with the new values, however, unfortunately I could not make it...
clear all;
x=[-7.5 -2.5 2.5 7.5] %
for i=1:3
xx(1,i)=2.5+x(i) % I need the 2.5 added only to [-7.5 -2.5 2.5] and also I need the output to be with the original vector included
% I mean I'd like the output to be
% xx(1,i)= [-7.5 -5 -2.5 0 2.5 5 7.5]
% I know i only = 3 and I need the output to be 9 elements but what can I do ??
end
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Korbinian Volgt am 8 Nov. 2019
Bearbeitet: Korbinian Volgt am 8 Nov. 2019
I am not sure what your exact intention is by +2.5, I guess what you want is to have an equally distributed vector with a step of 2.5 instead of 5. In general it's good practice to predefine vectorlength, so one approach would be:
x=[-7.5 -2.5 2.5 7.5];
xx = zeros(1,7);
for i=1:3
xx(1,2*i-1) = x(1,i);
xx(1,2*i) = x(1,i) + 2.5;
end
xx(1,end) = x(end)
But much easier would be to define your vector as equal distributed numbers from your minimum to the maximum value with the stepsize of 2.5:
xx = -7.5:2.5:7.5
Ali Tawfik am 8 Nov. 2019
Hi Korbinian,
actually david has answered what I meant, however,I have been trying to have output of 9 elements because later I will use this vector in plot...
I mean I need some of the elements to be repeated like the following:
[-7.5 -5 -2.5 -2.5 0 2.5 2.5 5 7.5]
Hope you understand, and try to help me!

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### Akzeptierte Antwort

David Hill am 8 Nov. 2019
xx=[x(1:3);x(1:3)+2.5];
xx=[xx(:)',x(4:end)];
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David Hill am 8 Nov. 2019
What elements to you want repeated? I don't understand what you are trying to do. What are you plotting against?
Ali Tawfik am 9 Nov. 2019
Hi,
I will plot them aganist vector of 9 elements, I would like to repeat element no#: 3 and 6
so it's -2.5 and 2.5.

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