Removing entries of vector indexed by odd integer.

2013 9 25
2 个回答
回答已采纳
7 次查看（30 天）

0 个投票

So, in a question we've been asked to define a vector "x" which begins at 1.5 and ends at -3.5 with 101 entries in between without the use of any loops. So, I used linspace(1.4, -3.5, 101) to do this. However the next part of the question requires you to create a matrix "y" which corresponds to "x" only with the entries indexed by an odd integer removed. How can you do this without using a loop? Is there a function for it? Thanks.

请先登录，再回答此问题。

 采纳的回答

Leah
Leah 2013-9-25

1 个投票

You just have to reference every other element of the vector you created.
x=linspace(1.4, -3.5, 101) ;
y=x(1:2:end);

1 个评论
显示 -1更早的评论 隐藏 -1更早的评论

David
David 2013-9-25
Will that not include elements 1 and 101 though, and they're odd indexes? Why wouldn't it be y = x(2:2:100);?

请先登录，再进行评论。

更多回答（1 个）

Matt J
Matt J 2013-9-25
编辑：Matt J 2013-9-25

1 个投票

x=linspace(1.4, -3.5, 101) ;
y=x;
y(1:2:end)=[];
or
y=x(2:2:end);

9 个评论
显示 7更早的评论 隐藏 7更早的评论

David
David 2013-9-25
y(1:2:end)=[]; or
y=x(2:2:end); seeing as these are two different lines of code, how is it that they work in the same way?
Matt J
Matt J 2013-9-25
Because deleting odd x(i) is equivalent to keeping even x(i).
David
David 2013-9-25
So, this y(1:2:end)=[] deletes the odd entries? Sorry for the basic questions. Literally only had our first lecture in this the other day.
Matt J
Matt J 2013-9-25
Why don't you try and find out ;)
David
David 2013-9-25
Hah. I would but I'm not in college and don't have MATLAB on my laptop. Would this y=x(2:2:end); not include the last element, which would be of index 103?
Leah
Leah 2013-9-25
David there is a student version of MATLAB available for $99. I ended up using MATLAB for lots of other courses, not just numerical analysis where it was required.
http://www.mathworks.com/academia/student_version/
Image Analyst
Image Analyst 2013-9-25
It gets elements, 2,4,6,8,10,12,14,........98,100,102. It can't get 104 since there is no 104, and since it doesn't get odd numbers, it won't get 103 even though it is "end" because it is odd. Does that explain it better?
David
David 2013-9-25
Brilliant! Thanks a million.

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Functional Programming 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