How to repeat the first number only

1 次查看（过去 30 天）
fyza affandi
fyza affandi 2018-12-7
编辑： Stephan 2019-1-2
Array a is given
a =[1]
How can I add 0 to the array depending on n.
n=1 --> a=[0 1]
n=2 --> a=[0 0 1]
n=3 --> a=[0 0 0 1]
and n can be changes to any number

请先登录，再回答此问题。

采纳的回答

madhan ravi
madhan ravi 2018-12-7
编辑：madhan ravi 2018-12-7
a = 1;
n = 2; % just an example n
a = [zeros(1,n) a]

更多回答（1 个）

Image Analyst
Image Analyst 2018-12-7
madhan's way is the best (how I'd do it), but I just want to show you a neat trick - that you can "grow" an array by simply assigning something to the last location (the location at the largest point that you want to grow it to):
a = 1; % Initial array.
n = 2; % just an example n
% a = [zeros(1,n) a] % Best way
a(n+1) = 0; % Enlarge array by appending zeros simply by assigning the last element.
a = fliplr(a) % Flipr it so that the 1 is on the right.
  5 个评论
显示 3更早的评论
Stephen23
Stephen23 2018-12-7
编辑：Stephen23 2018-12-7
Not just a neat trick, until R2015b allocating to the last element (and implicitly filling array with zeros) was faster than calling zeros:
https://www.mathworks.com/matlabcentral/answers/82989-fastest-way-to-fill-in-an-array#comment_161435
http://undocumentedmatlab.com/blog/preallocation-performance/

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Resizing and Reshaping Matrices 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