Sort elements of Array by given condition

Hello,

i have a vector n 480x1 and would like to sort the vector so that the condition

sum(([n ;0]-[0 ;n])>0)==68

is given. How could i do this? my approach was to realize a permutation of the vector until the condition is given. Unfortnely, this takes too much time.

Thanks in advance

[Dyuman Joshi]

That will depend upon the values of the vector.

You might not achieve that condition if all the values are monotonically increasing or decreasing.

Or do you want to change the indices of the values (jumble them up) to get this specific condition?

[Daniel]

Yes exactly! i want to change the indices of the values in the vector so that the condition ist true

[Dyuman Joshi]

Please attach your data using the paperclip button.

Although, I must say that it might be a challenging task to do so.

[Daniel]

There is the data. Thanks a lot!

[Torsten]

For that there are 68 pairs such that

n(i+1) - n(i) > 0, n(0) = 0 (i=0,...,67)

your array must have at least 68 different elements.

Yours has only 27.

Answer 1

[Matt J]

n=load('vector').xr;

m=numel(n);
n=n(randperm(m));

loc=find(([n ;0]-[0 ;n])>0);

n(loc(68):end)=sort(n(loc(68):end),'descend');

sum(([n ;0]-[0 ;n])>0)

ans = 68

Answer 2

[Sulaymon Eshkabilov]

load('vector.mat')
XR1 = [xr;0]; XR2 = [0;xr]; 
IND = (XR1-XR2)>0;
ii = 1;
S = 0;
while S~=68
    S(ii+1) = S(ii)+IND(ii);
    ii=ii+1;
end
fprintf('Summation is halted at %d step  and the sum is %d \n', ii, S(ii))    

Summation is halted at 226 step  and the sum is 68