I am working with a code that first defines a matrix and then changes some values of that matrix. For example: temp1 = zeros(5,5); temp2 = temp1; temp2[[1; 3]] = [4; 3]; I would expect that the values of matrix temp1 would remain unchanged. But somehow the values of matrix temp1 are the same as…

As Oscar says, temp2 = temp1 just creates a new variable temp2 that is a different name for temp1, not a new underlying object. Consider: julia> t1 = zeros(5, 5); julia> t2 = t1; julia> t2 === t1 true help?> === search: === == !== ===(x,y) -> Bool ≡(x,y) -> Bool Determine whether x and y…

If you don’t want this behavior, temp2.=temp1 will make a copy.

Many thanks, Oscar! temp2.=temp1 gave me an error, but temp2=copy(temp1) worked.

Understood perfectly now. Many thanks! I have to go over the code from the beginning to see if there are more instances like this. This reasoning is different from Matlab and it was unexpected to me. Thank you once again.

If you’re coming from MATLAB it might be useful to look at: Noteworthy Differences from other Languages · The Julia Language Incidentally, the topic of this thread is point 2 on the list :slight_smile:

Many, many thanks, Nils!! It will be a great help. Thank you once again.

Many thanks, Henrique! Vem muito a tempo :slight_smile:

Matrix values

New to Julia

Henrique_Becker October 7, 2020, 1:32pm 8

I am late, but I will shamelessly promote my post trying to build a simple mental model of why you should see Julia “variables” as labels, not boxes.

2 Likes

Topic		Replies	Views
When will the original value be changed with the copied value? New to Julia question	8	1645	April 21, 2020
Why making a change in a copy of a variable changes the original variable? New to Julia	16	4610	November 14, 2020
Why is Julia messing up my variables? New to Julia	9	956	January 16, 2020
Copy or view, issue New to Julia matrices , copy , views	1	256	February 19, 2024
Assignment of array elements New to Julia question	2	5334	February 1, 2018

Matrix values

Related topics