How to supplement the matrix?

1 次查看（过去 30 天）
Lev Mihailov
Lev Mihailov 2019-7-5
评论： Jan 2019-7-8
Hello! I cleaned my signal from emissions, it is in the form of a matrix, but there I used i-1, in consequence of which, instead of 1100, I now have 1099 values, how can I add the last value?\
for i = 1:length(d)-1 % Error 1100 1099
if g(i)-50>= g(i+1);
f(i)=g(i);
end
end
  6 个评论
显示 4更早的评论
Lev Mihailov
Lev Mihailov 2019-7-5
Cycle loop has nowhere
f = zeros(size(g));
% why do i need to convert to zeros?
The problem removed the outliers from the signal was 1099 values ​​(these are the positions of the maxima), but in the matrix there are 1100 values
Jan
Jan 2019-7-8
@Lev: |zeros()< does not convert anything to zeros. Please read the documentation:
doc zeros
to find out, that this is a pre-allocation of the output. Letting an array grow iteratively is extremely inefficient. Matlab has to allocation a new array in each iteration. So:
r = [];
for k = 1:1e6
r(k) = rand;
end
needs 8*1e6 bytes finally, but intermediately 8*sum(1:1e6) bytes are allocated: 4 TeraByte!
I do not understand the meaning of your comment. If you detect outliers by subtracting pairs elements, of course there is one element less in the output.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（2 个）

dpb
dpb 2019-7-5
Adding to Stephen's answer Matlab syntax, the crystal ball says
for i = 1:length(d)-1 % Error 1100 1099
if g(i)-50>= g(i+1);
f(i)=g(i);
end
end
becomes
f=zeros(size(g));
ix=diff(g)<-50;
f(ix)=g(ix);
Lev Mihailov
Lev Mihailov 2019-7-5
Still nothing happened, gives an error
Index exceeds matrix dimensions.
  5 个评论
显示 3更早的评论
dpb
dpb 2019-7-5
c can only have length(d)-1 elements in it...as has been said multiple times before, preallocate it to the size wanted or compensate that there will always be one less array element since you're dealing with diff() functionality that produces one less element by its very nature.
dpb
dpb 2019-7-5
编辑：dpb 2019-7-5
In
for chek = 1:length(d)-1
if g(chek )-50>= g(chek +1);
c(chek )=10;
else g(chek )+50 <= g(chek +1);
c(chek)=g(chek );
end
end
the else clause should be elseif it appears.
What is the value for c if abs(diff(g))<50?
Again, use Matlab array syntax; the above loop construct (presuming the "elseif" and zero for then missing "else" clause)
c=zeros(size(g)); % preallocate to same size as g array
ix=diff(g)<-50;
c(ix)=10;
ix=diff(g)>=50;
c(ix)=g(ix);
You need to define what happens in the other cases not satisfied...if they're to remain unchanged, then use
c=g;
for initialization instead of zeros

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

产品

Community Treasure Hunt

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

Start Hunting!

Translated by