Taking the last value of a matrix or vector

Hi. How can I take a last term of a vector - since my vector dimensions change -, and plug it in somewhere else in my code without keep changing the code?

for example right now I do v(6) to get the 6th term. How can I do it for nth term.... Thanks

Answer 1

[Walter Roberson]

v(end)

or

v(length(v))

[Jan]

In older MATLAB version, v(length(v)) has been _significantly_ faster then v(end):

x = rand(1, 100);

MATLAB 6.5:

tic; for i=1:1e6; y=x(end); clear('y'); end; toc

>> 8.31 sec

tic; for i=1:1e6; y=x(length(x)); clear('y'); end; toc

>> 6.45 sec

MATLAB 2009a:

tic; for i=1:1e6; y=x(end); clear('y'); end; toc

>> 10.72 sec

tic; for i=1:1e6; y=x(length(x)); clear('y'); end; toc

>> 11.06 sec

[Walter Roberson]

Were those timings all on the same system? If so that would imply that MATLAB has gotten much slower over the years ?

[Marcus]

In MATLAB R2015a, end is faster than length():

>> x = rand(1, 100);

>> tic; for i=1:1e6; y=x(end); clear('y'); end; toc

Elapsed time is 5.475081 seconds.

>> tic; for i=1:1e6; y=x(length(x)); clear('y'); end; toc

Elapsed time is 5.705095 seconds.

[Sangbok Lee]

R2021a

I've tried it several times.

"end" is always slightly faster than "length()"

I think "end" works the same way using index numbers.

>> x=rand(10000);

>> tic; for i=1:1e7; y=x(end); clear y; end; toc

Elapsed time is 21.722168 seconds.

>> tic; for i=1:1e7; y=x(length(x),length(x)); clear y; end; toc

Elapsed time is 22.073104 seconds.

>> tic; for i=1:1e7; y=x(10000,10000); clear y; end; toc

Elapsed time is 21.818949 seconds.