How to trim down data in an array

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)
    
    

[Ünal Dikmen]

you can do it simply as below:

...

red_A = A(1:tt:end-1) + A(end);

[Walter Roberson]

@Ünal Dikmen

    a = 1;
    b = 200;
    A = (b-a).*rand(1000,1) + a;
% 
tt = floor(length(A)/10)

tt = 100

red_A = A(1:tt:end-1);
size(red_A)

ans = 1×2

10 1

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A(end) added to red_A will produce a vector of the same length as red_A, so A(1:tt:end-1) + A(end) would be a vector of length 10. But the task was to produce a vector of length 100.

[Ünal Dikmen]

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]

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.

Answer 1

[Walter Roberson]

tt = floor(linspace(1,length(A),100));
red_A = A(tt) ;

[Telema Harry]

Thank you

[Ünal Dikmen]

this code also an elegant way :)

Answer 2

[KSSV]

 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) ; 

[Telema Harry]

Thank you