loc

Syntax

loc(obj, rowFilter, [colFilter], [view=false])

Arguments

obj is a matrix object. It can be a standard matrix, an indexed series or an indexed matrix.

rowFilter/colFilter can be:

• a Boolean vector - the rows/columns marked as true will be returned. The length of the vector must match the number of rows/columns of obj.

• a scalar, a vector or a pair whose data type is compatible with the row/column labels of obj. A pair indicates the selection range (both upper bound and lower bound are inclusive).

Note:

• If rowFilter/colFilter is a pair, then obj must be an indexed series or an indexed matrix.

• Data type compatibility rules:

  • INT, SHORT, LONG and CHAR are compatible

  • FLOAT and DOUBLE are compatible

  • STRING and SYMBOL are compatible

view is a Boolean value. The default value is false indicating the result will be a copy of the original matrix (deep copy). If set to true, the result will be a view on the original matrix (shallow copy) and changes made to the original matrix will be reflected in the view.

Details

Access a group of rows and columns of a matrix by label(s) or a boolean vector. Return a copy or a view of the original matrix.

Examples

$ m=rand(12, 3:4)
$ m;

col1	col2	col3	col4
3	10	6	5
4	11	6	0
7	2	1	8

$ a = m.loc(colFilter=[true, true, true, false], view=true)
$ b = m.loc(colFilter=[true, true, true, false], view=false)
$ a;

col1	col2	col3
3	10	6
4	11	6
7	2	1

$ b;

col1	col2	col3
3	10	6
4	11	6
7	2	1

// a view reflects changes made to the original matrix whereas a copy doesn't
$ m[0,0] = -1
$ a;

col1	col2	col3
-1	10	6
4	11	6
7	2	1

$ b;

col1	col2	col3
3	10	6
4	11	6
7	2	1

$ m = rand(48, 6:8)
$ m;

col1	col2	col3	col4	col5	col6	col7	col8
27	31	47	21	12	43	22	11
3	20	13	37	3	46	27	27
13	5	14	11	26	42	4	18
45	9	31	33	12	19	42	17
2	19	30	25	36	27	21	6
9	36	15	10	29	37	31	42

// filter with Boolean values
$ m.loc(rowFilter=[true, true, false, false, true, false])

col1	col2	col3	col4	col5	col6	col7	col8
27	31	47	21	12	43	22	11
3	20	13	37	3	46	27	27
2	19	30	25	36	27	21	6

$ m.loc(colFilter=[true, true, false, false, true, false, false, true])

col1	col2	col3	col4
27	31	12	11
3	20	3	27
13	5	26	18
45	9	12	17
2	19	36	6
9	36	29	42

// filter with labels
$ m.rename!(`A`A`B`A`B`B, 2022.01.01 + 0..7)
$ m;

label	2022.01.01	2022.01.02	2022.01.03	2022.01.04	2022.01.05	2022.01.06	2022.01.07	2022.01.08
A	27	31	47	21	12	43	22	11
A	3	20	13	37	3	46	27	27
B	13	5	14	11	26	42	4	18
A	45	9	31	33	12	19	42	17
B	2	19	30	25	36	27	21	6
B	9	36	15	10	29	37	31	42

$ m.loc(rowFilter=`A);

label	2022.01.01	2022.01.02	2022.01.03	2022.01.04	2022.01.05	2022.01.06	2022.01.07	2022.01.08
A	27	31	47	21	12	43	22	11
A	3	20	13	37	3	46	27	27
A	45	9	31	33	12	19	42	17

$ m.loc(colFilter=2022.01.02);

label	2022.01.02
A	31
A	20
B	5
A	9
B	19
B	36

$ m.loc(rowFilter=`B, colFilter=2022.01.03)

label	2022.01.03
B	14
B	30
B	15

Related function: at