How to trim down data in an array

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Telema Harry
Telema Harry 2021-11-10
编辑： Walter Roberson 2025-7-8
Hi,
I have a column vector containing 1000 element.
I really need to reduce the size of the vector to 100 to be able to use it further in my program.
The reduced data must contain the first and last element of the original vector.
My current code is shown below. It does not capture the last element.
Thanks for your help.
a = 1;
b = 200;
A = (b-a).*rand(1000,1) + a;
%
tt = floor(length(A)/10);
if tt == 0
tt = 1;
end
red_A = A(1:tt:end)
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Ünal Dikmen
Ünal Dikmen 2025-7-8
编辑：Walter Roberson 2025-7-8
yes, you are right. I thought you wanted to get especially the last element in this vector. if you want to get a constant number of elements (100 as in this example) in a vector, you can use code below:
noel = 100;
npts = numel(A);
interval = ceil(npts-1)/noel;
red_A=A(1:interval:npts);
using this code you can get the number of elements noel in the vector.
Walter Roberson
Walter Roberson 2025-7-8
Ran in:
a = 1;
b = 200;
A = (b-a).*rand(1000,1) + a;
noel = 100;
npts = numel(A);
interval = ceil(npts-1)/noel;
red_A=A(1:interval:npts);
Warning: Integer operands are required for colon operator when used as index.
size(red_A)
ans = 1×2
101 1
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Your code has the warning about non-integer increment, and produces a vector that is 1 element too long
red_A(end) == A(end)
ans = logical
1
But at least the last element appears to be correct.

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采纳的回答

Walter Roberson
Walter Roberson 2021-11-10
编辑：Walter Roberson 2025-7-8
tt = floor(linspace(1,length(A),100));
red_A = A(tt) ;

更多回答（1 个）

KSSV
KSSV 2021-11-10
a = 1;
b = 200;
A = (b-a).*rand(1000,1) + a;
x1 = 1:length(A) ;
x2 = linspace(1,length(A),100) ;
Anew = interp1(x1,A,x2) ;

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