Delete some specific numbers from an array

2019 10 2
2 个回答
更新时间：2019 10 3
1 次查看（30 天）

0 个投票

So, the problem is like this. I have an array of random numbers. For example [10 9 5 5 7 3 5 8 3 5 6 3 7 10 ]. First, I have to delete some of the numbers to make any point's value can not between its adjecent numbers. For example 9 is between 10 and 5, so I will delete 9. I tried to use a for loop but that does not work.

2 个评论
显示 无 隐藏 无

Walter Roberson
Walter Roberson 2019-10-2
Hint: sign(diff(TheVector)) will be the same for two entries in a row if the middle value is between the two other values (or if the three values are all equal)
Andrei Bobrov
Andrei Bobrov 2019-10-3
We delete 7, 7 is between 3 ans 10?

请先登录，再进行评论。

请先登录，再回答此问题。

回答（2 个）

Andrei Bobrov
Andrei Bobrov 2019-10-2
编辑：Andrei Bobrov 2019-10-3

0 个投票

A = [10 9 5 5 7 3 5 8 3 5 6 3 7 10 ];
B = sign(diff(A(hankel(1:3,3:numel(A)))',1,2));
out = A( [true; prod(B,2) ~= 1 ; true] );

2 个评论
显示 无 隐藏 无

Rongyu Chu
Rongyu Chu 2019-10-3
My final purpose is not just delete 9 among 10 and 5. This is just an example. I will have a dat file which contians over 10,000 numbers and I need it to process automatically. Thank you for your help.

请先登录，再进行评论。

Rongyu Chu
Rongyu Chu 2019-10-3

0 个投票

So, here is the cide I wrote.
N = load('exp.dat');
len = length(N);
for i = 2:(len-3)
if N(i+1)>N(i)>N(i-1)
N(i) = [];
len = len - 1;
%i = i - 1;
elseif N(i+1)<N(i)<N(i-1)
N(i) = [];
len = len - 1;
%i = i - 1;
end
end
I tired to use if sentence to compare the value and delete those numers whose value is in the middle of its adjcent numbers. However, this code does not work well. I am wondering why.

3 个评论
显示 1更早的评论 隐藏 1更早的评论

Walter Roberson
Walter Roberson 2019-10-3
A<B<C does not mean that B must be in the range A to C. Instead it is ((A<B)<C) where the A<B returns 0 for false and 1 for true, and that 0 or 1 is compared to C.
Rongyu Chu
Rongyu Chu 2019-10-3
thank you. I realized that problem. But now I found a new problem. After I delete some numbers from an array, the arrat size gonna change. So it's not always len-1. But, how should I update that information ?
Walter Roberson
Walter Roberson 2019-10-3
Index from highest to lowest so that when you delete, you do not need to examine the entries that "fell down".

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by