MATLAB Answers

modify a row of an array within a function

조회 수: 17(최근 30일)
Ernst Reißner
Ernst Reißner 2021년 5월 18일
편집: James Tursa 2021년 5월 18일
I have a 2 dimensional array arr and at various places i want to replace the ii-th row.
So I would like to write a function
function arr = replace(arr, ii)
and call that, e.g. in a loop but also with fixed ii.
My problem is that i fear that all of arr is copied then.
I just want a passed by reference and replace the row.
Is this feasable??
  댓글 수: 1
Stephen
Stephen 2021년 5월 18일
"My problem is that i fear that all of arr is copied then."
Have you checked this?

댓글을 달려면 로그인하십시오.

답변(2개)

KSSV
KSSV 2021년 5월 18일
If a is an array of size m*n, you can repalce i'th row with a row matrix b of size 1*n using:
a(i,:) = b ;
  댓글 수: 1
Ernst Reißner
Ernst Reißner 2021년 5월 18일
I know.
that is exactly what I would do within the function replace(...).
But my question is how i can avoid that when invoking replace all of a is copied
although within replace i just replace a single row.
I know, if I just read from a, it is not copied, but it is if i modify.
RIght now i wonder whether if i could define a to be an array of arrays,
accessing as a(ii)(jj).. this would spare someting. but far from ideal.

댓글을 달려면 로그인하십시오.


James Tursa
James Tursa 2021년 5월 18일
편집: James Tursa 2021년 5월 18일
This can sometimes be done inplace depending on how you write the function and how you call the function. One requirement is your function needs to be called from within another function (easy to do). Another requirement is that your variable can't be shared with another variable (not easy to guarantee unfortunately). See this blog:

Community Treasure Hunt

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

Start Hunting!

Translated by