eachAt(@)

X@index

eachAt(X, index)

X can be a scalar/vector(including tuple)/matrix/table/dictionary/pair/unary function.

index can be a Boolean expression/scalar/vector/tuple/pair.

If index is a Boolean expression, returns the elements in X that satisfy the condition specified by index (i.e., index = true). If not, returns the elements in X with the corresponding index.

If X is a function, index is used as an argument of X.

The differences between eachAt and at lie in:

(1) when index is a tuple (e.g., index = (0, 1) ), and X is a tuple of vectors:

• X @ (0, 1) returns the first and second elements in X.

• X at (0, 1) returns the value at position 1 of the first element in X.

(2) when X is a function:

• Only unary function can be specified for eachAt.

• Function with one or multiple parameters can be specified for at.

The following table shows the data forms supported by X and index.

v = 3.1 2.2 4.5 5.9 7.1 2.9
eachAt(v, v > 3)
[3.1,4.5,5.9,7.1]
    
v @ 1:3
[2.2,4.5]

v @ (:4)
[3.1,2.2,4.5,5.9]
v @ (3:)
[5.9,7.1,2.9]

// the difference between eachAt and at when index is specified as a tuple
tp = [2.3 2.1 2.2, 3.1 2.9 2.8, 5.7 6.9]
tp @ [1 2 3, 0 1 2]
(([3.1,2.9,2.8],[5.7,6.9],),([2.3,2.1,2.2],[3.1,2.9,2.8],[5.7,6.9]))
tp at [1 2 3, 0 1 2]
([3.1,2.9,2.8],[5.7,6.9,],)

sum @ 6 2 3 NULL 2 -3
10

// seq(...) must be enclosed in parentheses since its priority is lower than @
sum @ (1..10)
55

Related functions: at