How to deal with repeated data in a column of a table

Question

QIAO WANG 2019-10-30

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/488311-how-to-deal-with-repeated-data-in-a-column-of-a-table

评论： QIAO WANG 2019-11-13

Hey,

I'm currently trying to process a table. What I want is to extract a sequence from a column of it. Before I used unique but apparently the result wasn't what I intended for.

An example of the table could be like below. I want to extract [22 24 22] for vid 59. However, unique only gave me [22 24], which is not what I want. So, I hope I've explained my question well. Appreciate your advice on this!!

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Cyrus Tirband 2019-10-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/488311-how-to-deal-with-repeated-data-in-a-column-of-a-table#answer_398972

编辑：Cyrus Tirband 2019-10-30

在 MATLAB Online 中打开

It sounds like you're looking to remove repeating elements that are adjecent. If that is the case, you can test your array for differences between each element and remove the parts where the difference is 0.

If your array is named A, then:

A(diff(A)==0) = []

8 个评论
显示 6更早的评论隐藏 6更早的评论

QIAO WANG 2019-11-11

在 MATLAB Online 中打开

Hey Cyrus.

I've got another data processing problem. So could you please have a look?

As I mentioned earlier, I'm dealing with a table and it looks like this. I've shortened it a bit to show here. In my last question, I'd like to extract 19 22 24 22 24, which was successful thanks to your help and that was for a different purpose. Now, based on Table I, I'm going to get the first row when a BSid first appeared and the last row when the same BSid lastly appeared. For example, I'd like to obtain a table which looks like Table II. I've been thinking about this for a while but unfortunately, no good idea has come into my mind.

So, I wish you could have some good idea about this and thank you in advance.

Table I:
     ID      Time         BSid
    08:47:31     19 
    08:47:32     19 
    08:47:33     19 
    08:47:34     19 
    08:47:35     22 
    08:47:36     22 
    08:47:37     22 
    08:47:38     22 
    08:47:39     22  
    08:47:45     24 
    08:47:46     24 
    08:47:47     24 
    08:47:48     24 
    08:47:49     24 
    08:47:50     22 
    08:47:51     22 
    08:47:52     22 
    08:48:00     22 
    08:48:01     24 
    08:48:02     24 
    08:48:03     24 
    08:48:04     24 
    08:48:05     24 
Table II:
     ID      Time         BSid
    08:47:31     19 
    08:47:34     19 
    08:47:35     22 
    08:47:39     22  
    08:47:45     24 
    08:47:49     24 
    08:47:50     22 
    08:48:00     22 
    08:48:01     24 
    08:48:05     24

Cyrus Tirband 2019-11-12

编辑：Cyrus Tirband 2019-11-12

在 MATLAB Online 中打开

Hi Qiao,

You can use a similar approach. In this case, you have two requirements for the elements that you want to remove. Not only must the finite difference diff(A) be equal to zero (no repeating elements), the second finite difference, diff(diff(A)) must also be equal to zero (no change in slope). So, and(diff(A) ==0, diff(diff(A)) == 0) is the set that must be removed. Using de morgan's law this can be written a bit more succinctly as ~or(diff(A), diff(diff(A))).

Of course, you always want the first index to be included, so you need to enter that one manually as a 1, since diff(diff(A)) will be one index shorter.

In code:

A = [22; 22; 22; 24; 24; 24; 22; 22; 22];
A(~or(diff(A),[1; diff(diff(A))])) = []
A =
    22
    22
    24
    24
    22
    22

QIAO WANG 2019-11-13

Thank you Cyrus. Actually, before you replied to me, I also raised a question in the community and got a good one. Anyway, yours is a brilliant idea! Worked for me too.

请先登录，再进行评论。