slice

Syntax

slice(obj, index)

or

slice(obj, rowIndex, [colIndex])

which is equivalent to

obj[index] or obj[rowIndex, colIndex]

Arguments

obj can be an array vector, a matrix or a table.

index, rowIndex and colIndex can be scalar/vector/pair indicating the row or column index. If index, rowIndex or colIndex is a pair, it indicates the range of index which is left-closed and right-open.

Details

For slice(obj, index):

  • If obj is an array vector and

    • index is a scalar, it returns a vector indicating a column;

    • index is a vector, it returns an array vector of selected rows;

    • index is a pair, it returns an array vector of selected columns.

  • If obj is a matrix and

    • index is a scalar, it returns a vector indicating a column.

    • index is a vector or a pair, it returns a matrix of selected columns.

  • If obj is a table and

    • index is a scalar, it returns a dictionary indicating a row.

    • index is a vector or a pair, it returns a table of selected rows.

For slice(obj, rowIndex, [colIndex]):

  • If obj is an array vector and

    • rowIndex and colIndex are both scalars, it returns a vector indicating a column;

    • rowIndex is a scalar and colIndex is a pair (or vise versa), it returns an array vector of selected rows and columns;

    • rowIndex and colIndex are both pair, it returns an array vector of selected rows and columns.

  • If obj is a matrix and

    • rowIndex and colIndex are both scalars, it returns a scalar indicating the value of specified element of the matrix.

    • rowIndex is a scalar and colIndex is a pair (or vise versa), it returns a submatrix of selected rows and columns.

    • rowIndex and colIndex are both vectors or pairs, it returns a submatrix of selected rows and columns.

  • If obj is a table and

    • rowIndex and colIndex are both scalars, return a scalar indicating the value of specified element of the table.

    • rowIndex is a scalar and colIndex is a pair (or vise versa), it returns a table of selected rows and columns.

    • rowIndex and colIndex are both vectors or pairs, it returns a table of selected rows and columns.

Note:

  • To get a particular row or column from a table, consider using function col or row.

  • When index, rowIndex or colIndex specifies the index range of an array vector or a matrix, if the values are not within [0, size(X)-1], the corresponding results are NULL values.

Examples

If obj is a matrix:

m=1..9$3:3
m.slice(0);
// output
[1,2,3]
    
m.slice([0]);
#0
1
2
3 
m.slice(0:2);
#0 #1
1 4
2 5
3 6 
m.slice(0 2);
#0 #1
1 7
2 8
3 9 
m.slice(0,1);
// output
 4

m.slice(0 1,0 1);
#0 #1
1 4
2 5 
m.slice(1:2,1:2);
#0
5

If obj is a table:

t=table(`A`B`C as sym,2018.01.01..2018.01.03 as date,10 48 5 as val)
t.slice(0);
// output
val->10
date->2018.01.01
sym->A
t.slice([0]);
sym date val
A 2018.01.01 10 
t.slice(0 1);
sym date val
A 2018.01.01 10
B 2018.01.02 48 
t.slice(0:1);
sym date val
A 2018.01.01 10 
t.slice(0,1);
// output
2018.01.01
 
t.slice(0 1,0 1);
sym date
A 2018.01.01
B 2018.01.02 
t.slice(1:2,1:2);
date
2018.01.02

If obj is an array vector:

av =array(DOUBLE[], 0, 10).append!([1.0, 2.1 4.1 6.8, 0.5 2.2 2]);
av[1] 
// output
[,4.1,2.2]

av[1,1]
// output
[4.1]

av[1:3,1:3] 
// output
[[4.1,6.8],[2.2,2]]