How does Squeeze work?

Question

Negar 2011-5-1

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/6560-how-does-squeeze-work

编辑： Stephen23 2020-11-19

采纳的回答： Matt Fig

Hello all,

Can anybody explain me what Squeeze is used for? I have read about it in MATLAB help but I am still confused !

Thanks a lot :-)

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt Fig 2011-5-1

6
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/6560-how-does-squeeze-work#answer_9053

在 MATLAB Online 中打开

In addition to what James said, just look at an example or two. Look what happens to the dimensions of A with squeeze, particularly what happens to the dimension with the 1 (so-called singleton dimensions).

A = rand(6,7,1,2);  % size(A) = [6 7 1 2]
size(squeeze(A))
A = rand(1,6,7,2);
size(squeeze(A))
A = rand(6,7,1,2);
size(squeeze(A))

Now try it with two (or more) 1 (singleton) dimensions.

A = rand(6,7,1,2,1,7);  % size(A) = [6 7 1 2 1 7]
size(squeeze(A))
A = rand(1,6,1,7,2,1,8); % size(A) = [1 6 1 7 2 1 8]
size(squeeze(A))
A = rand(6,1,7,1,2);
size(squeeze(A))

I think you see the pattern. Now that you see what is going on with the dimensions, look at the data (using simpler examples):

A = reshape(randperm(6),2,1,3)  % Look at this data
squeeze(A) % Now look at it.
A = reshape(randperm(6),1,2,3)
squeeze(A)

So wee see that SQUEEZE reads off the columns of A while creating an array with no singleton dimensions.

6 个评论
显示 4更早的评论隐藏 4更早的评论

Swati Sarangi 2020-11-19

在 MATLAB Online 中打开

Hi ,

@Matt Fig,

I'm getting an error in line 2 of the following code snippet while trying to implement it in my MATLAB.

A = rand(6,7,1,2);  % size(A) = [6 7 1 2]
size(squeeze(A))
A = rand(1,6,7,2);
size(squeeze(A))
A = rand(6,7,1,2);
size(squeeze(A))

Stephen23 2020-11-19

编辑：Stephen23 2020-11-19

在 MATLAB Online 中打开

@Swati: your code works without error:

A = rand(6,7,1,2);  % size(A) = [6 7 1 2]
size(squeeze(A))
ans = 1×3
     6     7     2
●
A = rand(1,6,7,2);
size(squeeze(A))
ans = 1×3
     6     7     2
●
A = rand(6,7,1,2);
size(squeeze(A))
ans = 1×3
     6     7     2
●

If you are getting an error then please show us the complete error message. This means all of the red text.

请先登录，再进行评论。

Answer 2

James Tursa 2011-5-1

3
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/6560-how-does-squeeze-work#answer_9039

The squeeze function is similar to reshape in that it changes the dimensions of a variable without moving any of the data in memory. The total number of elements and their ordering in memory remain the same. For squeeze, the new dimensions are simply the old dimensions with all singleton (==1) dimensions removed (except 2D inputs are left as is).

As for what it is used for, it may be that the result of some algorithm has left you with a 1x2x1x3 matrix and you need to feed that to a function that needs a 2D input. So you could use squeeze on it to get the 2D input as a 2x3 matrix.