如何为 J 中的三列数字编写函数？

Question

I need to write a function that I just need to input three cols of number and it will out puts a col of number. So they can calculate in each row and finally get just one row number. For example,X= 1 2 3, Y = 2 3 4, Z= 0 1 2, calculate (xz)/(yz), so the output is 0.5 0.5 0.5

Answer 1

I think that you have pretty much stated how it could be solved if you convert your math notation to J (also use =: as assignment rather than = )

   X=: 1 2 3
   Y=: 2 3 4
   Z=: 0 1 2
   (X-Z)%(Y-Z) NB. doesn't need second parenthesis pair (X-Z)%Y-Z also works
0.5 0.5 0.5

Reading again you wanted columns of numbers instead of rows, so we'll just change the rows to columns using monadic ,. "Ravel Items" which takes each item and makes it a row. In this case the each item is an atom and the rows are made into columns and the result is a column.

   ex=: ,.X
   why=: ,. Y
   zed=: ,. Z
   ex
1
2
3
   why
2
3
4
   zed
0
1
2
   (ex-zed)%why-zed
0.5
0.5
0.5

Answer 2

If this is related to your other question , you can box or shape the arguments to pass arbitrary shapes:

 f =: 3 : 0                                                                                                                                                 
'x y z' =. y
(x-z)%(y-z)                                                                                                                                                  
)

f 1 2 3
 2    
f (1 2 3);(2 3 4);(0 1 2)
 0.5 0.5 0.5

f (2 3 $ 5 4);(2 3$ 6 4 2);(2 3$ 7 5)
 2        1      0.4
_1 0.666667 0.333333


f i.3 2 4 3  NB. Input shape (3 a b c...), output shape a b c...
 2 2 2
 2 2 2
 2 2 2
 2 2 2

 2 2 2
 2 2 2
 2 2 2
 2 2 2