I've used Pandas a bit and it certainly works well, but there are a lot of library functions to learn while J seems to basically be learn the two uses for every symbol and know how to do all math stuff ;).
I'm always impressed to see derivative and both matrix inversion & transpose as elementary operations instead of googling for a library that is most likely poorly documented. Furthermore, since the vector is the basic data type, things like matrices crop up a lot more in J & APL. In Python they are for scientific pursuits. In J they will often crop up even if you're writing a blackjack game. I think this is why it doesn't appeal to many programmers without a strong mathematics background, but it's very appealing to those who have that kind of background and grow tired of writing incessant loops.
I'm always impressed to see derivative and both matrix inversion & transpose as elementary operations instead of googling for a library that is most likely poorly documented. Furthermore, since the vector is the basic data type, things like matrices crop up a lot more in J & APL. In Python they are for scientific pursuits. In J they will often crop up even if you're writing a blackjack game. I think this is why it doesn't appeal to many programmers without a strong mathematics background, but it's very appealing to those who have that kind of background and grow tired of writing incessant loops.