How can I get a first value of each index from the other column?

1 次查看（过去 30 天）
Jaehwi Bong
Jaehwi Bong 2019-9-24
评论： Rik 2019-9-24
I have this kind of data. First column and seconds column refer to an index and x value relatively.
data = [1 200; 1 201; 1 202; 1 201; 2 301; 2 313; 2 311; 3 401; 3 452; 3 433; 3 405; 4 504; 4 303; 4 604; 4 703; 5 600; 5 700; 5 606; 5 703; 5 905; 5 444;];
I want to have first value of 2nd colum of each index.
I'd like to have this kind of data that has half length (or tird whatever ratio) of index.
data = [1 200; 2 301;3 401;4 604;5 600;];
If anyone can help, it would be greatly appreciated.
Thank you!

请先登录，再回答此问题。

采纳的回答

Rik
Rik 2019-9-24
Use unique to get the list of first indices, the use either find or min in a loop.
  2 个评论
Jaehwi Bong
Jaehwi Bong 2019-9-24
编辑：Jaehwi Bong 2019-9-24
Thank you for your answer!
After I use the unique function, I'd like to get the corresponding values of second colum to the first value of first column. I don't want to use min.
for i = 1: max(col1)
col2(col1==i); %how can I get the 1st value of every iteration col2?
end
Could you give me advice again,please?
Rik
Rik 2019-9-24
This doesn't exactly match your output, but I suspect that could be a typo.
data = [1 200; 1 201; 1 202; 1 201; 2 301; 2 313; 2 311; 3 401; 3 452; 3 433; 3 405; 4 504; 4 303; 4 604; 4 703; 5 600; 5 700; 5 606; 5 703; 5 905; 5 444;];
col1=unique(data(:,1));
output=col1;
for n=1:numel(col1)
output(n,2)=data(find(data(:,1)==col1(n),1),2);
end
clc,disp(output)

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 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