How to filter a matrix with an index？

[wujilingfeng]

I want to filter a matrix with index info and record it's index for other use, so how to filter a matrix with an index？

[dpvanbalen]

The easiest way is probably to first use indexed to match each element with its index, and then use filter on that matrix. Does this help? If not, can you elaborate a bit more on what exactly you would like this function to do?

[wujilingfeng]

The easiest way is probably to first use indexed to match each element with its index, and then use filter on that matrix. Does this help? If not, can you elaborate a bit more on what exactly you would like this function to do?

I use the same principle as you, but the details are different