lists@lowfrequency.or

Bug report: Under certain circumstances (one in particular), a 

jit.matrix will not interpolate properly.

When trying to interpolate to a single dimension (e.g. a 1xN matrix), 

I expect the result to be a single-column matrix with each cell of 

the column containing an average of the entire row it belongs to.

the result is not an interpolated matrix but rather the 1st column of 

the original matrix with no interpolation.

(Read in a movie or image, and observe the results. You should 

notice that the jit.submatrix output is conspicuously identical to 

Bug report:  Under certain circumstances (one in particular), a  
jit.matrix will not interpolate properly.
Max/jitter 4.5.7/1.5.2
OS X 10.4.6

When trying to interpolate to a single dimension (e.g. a 1xN matrix),  
I expect the result to be a single-column matrix with each cell of  
the column containing an average of the entire row it belongs to.

When trying to interpolate to a single dimension (e.g. a 1xN matrix),  
the result is not an interpolated matrix but rather the 1st column of  
the original matrix with no interpolation.

Example patch:
(Read in a movie or image, and observe the results.  You should  
notice that the jit.submatrix output is conspicuously identical to  
the jit.matrix output)

bug-matrix-interpolation-doesnt-work-properly

Oops, the jit.submatrix should be @dim 1 240, NOT @dim 1 512. But 

the result is the same, no need to change it, I just didn't want to 

confuse anyone. (Sorry, copied and pasted out of another patch).

Oops, the jit.submatrix should be @dim 1 240, NOT @dim 1 512.  But  
the result is the same, no need to change it, I just didn't want to  
confuse anyone.  (Sorry, copied and pasted out of another patch).

> When trying to interpolate to a single dimension (e.g. a 1xN 

> matrix), I expect the result to be a single-column matrix with each 

> cell of the column containing an average of the entire row it 

> matrix), the result is not an interpolated matrix but rather the 

> 1st column of the original matrix with no interpolation.

This is not a bug. This is how pointwise linear interpolation works. 

It is not an averaging filter. For more on the subject, I'd suggest 

If you want to average all elements in a column/row, etc, I would 

suggest you iterate, downsampling by two and averaging each time. 

Below is an example, but it only works exactly right for power of two 

>
> Expected behavior:
> When trying to interpolate to a single dimension (e.g. a 1xN  
> matrix), I expect the result to be a single-column matrix with each  
> cell of the column containing an average of the entire row it  
> belongs to.
>
> Observed behavior:
> When trying to interpolate to a single dimension (e.g. a 1xN  
> matrix), the result is not an interpolated matrix but rather the  
> 1st column of the original matrix with no interpolation.

This is not a bug. This is how pointwise linear interpolation works.  
It is not an averaging filter. For more on the subject, I'd suggest  
searching online.

If you want to average all elements in a column/row, etc, I would  
suggest you iterate, downsampling by two and averaging each time.  
Below is an example, but it only works exactly right for power of two  
matrices.

Sorry, I misunderstood what the effects of interpolation would 

actually be - sometimes you don't realize that you have the wrong 

impression of something until you've actually tried to code it...

Thanks for the example patch, it's very helpful.

Sorry, I misunderstood what the effects of interpolation would  
actually be - sometimes you don't realize that you have the wrong  
impression of something until you've actually tried to code it...

BUG: matrix interpolation doesn't work properly