eachAt(@)
Syntax
X@index
eachAt(X, index)
Arguments
X can be a scalar/vector(including tuple and array vector)/matrix/table/dictionary/pair/unary function.
index can be a Boolean expression/scalar/vector/tuple/array vector/pair.
Details
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.
X/index | Boolean expression | scalar | vector | array vector | tuple | pair |
---|---|---|---|---|---|---|
scalar | √ | √ | √ | × | √ | √ |
vector | √ | √ | √ | √ | √ | √ |
tuple | √ | √ | √ | × | √ | √ |
array vector | √ | √ | √ | × | √ | √ |
matrix | √ | √ | √ | × | √ | √ |
table | √ | √ | √ | × | √ | √ |
dictionary | × | √ | √ | × | √ | × |
pair | √ | √ | √ | × | √ | √ |
function | √ | √ | √ | √ | √ | √ |
Examples
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