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How do I add values to a vector?

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Gabriel Aguirre
Gabriel Aguirre on 12 Dec 2023
Commented: Voss on 12 Dec 2023
How do I add values to a vector? I have the vector gdl_off = [1,2,14] and the vector X with 11 positions. I want the values in the positions specified by gdl_off to be 0, but if I use X(gdl_off,:) = 0, it only replaces the existing values.
gld_off = [1,2,14];
X = Kg_cut\F_cut;
X(gdl_off,:) = 0
but i have this
0
0
0.000248324742039762
-0.000614863156129983
0.000173205080756888
-0.000715692193816531
0.000207846096908266
-0.000735692193816530
9.80854194740139e-05
-0.000614863156129983
0.000346410161513776
0
0
0
and my original X is
0.000138564064605510
-0.000735692193816531
0.000248324742039762
-0.000614863156129983
0.000173205080756888
-0.000715692193816531
0.000207846096908266
-0.000735692193816530
9.80854194740139e-05
-0.000614863156129983
0.000346410161513776
  1 Comment
jessupj
jessupj on 12 Dec 2023
if you only want it to replace values, but NOT add new elements to the vector if you specify assignment to non-existing entries, then limit the assignment indices to the current length of the vector:
x( intersect(gld_off,1:numel(x)) ,:) = 0
otherwise, i'm not sure what you're after or what you're expecting.

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Accepted Answer

Voss
Voss on 12 Dec 2023
If you want to insert a zero element at each of the locations specified by gld_off, in turn, you can do this:
X = [0.000138564064605510;-0.000735692193816531;0.000248324742039762;-0.000614863156129983;0.000173205080756888;-0.000715692193816531;0.000207846096908266;-0.000735692193816530;9.80854194740139e-05;-0.000614863156129983;0.000346410161513776];
gld_off = [1,2,14];
for ii = 1:numel(gld_off)
X = [X(1:gld_off(ii)-1); 0; X(gld_off(ii):end)];
end
disp(X)
1.0e-03 * 0 0 0.1386 -0.7357 0.2483 -0.6149 0.1732 -0.7157 0.2078 -0.7357 0.0981 -0.6149 0.3464 0
However, the following is more efficient when you need to insert a large number of elements:
X = [0.000138564064605510;-0.000735692193816531;0.000248324742039762;-0.000614863156129983;0.000173205080756888;-0.000715692193816531;0.000207846096908266;-0.000735692193816530;9.80854194740139e-05;-0.000614863156129983;0.000346410161513776];
gld_off = [1,2,14];
NX_new = numel(X)+numel(gld_off);
X_new = zeros(NX_new,1);
X_new(setdiff(1:NX_new,gld_off)) = X;
X = X_new;
disp(X)
1.0e-03 * 0 0 0.1386 -0.7357 0.2483 -0.6149 0.1732 -0.7157 0.2078 -0.7357 0.0981 -0.6149 0.3464 0

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