APPLY_INVERSE_SVD

Transforms the data back to the original domain.

Transforms the data back to the original domain. This essentially computes the approximated version of the original data by multiplying three matrices: matrix U (input to this function), matrices S and V (stored in the model).

Syntax

APPLY_INVERSE_SVD ( 'input-columns'
        USING PARAMETERS model_name = 'model-name'
            [, match_by_pos = match-by-position]
            [, exclude_columns = 'excluded-columns']
            [, key_columns = 'key-columns'] )

Arguments

input-columns
Comma-separated list of columns to use from the input relation, or asterisk (*) to select all columns. The following requirements apply:

  • All columns must be a numeric data type.

  • Enclose the column name in double quotes if it contains special characters.

Parameters

model_name

Name of the model (case-insensitive).

match_by_pos

Boolean value that specifies how input columns are matched to model features:

  • false (default): Match by name.

  • true: Match by the position of columns in the input columns list.

exclude_columns

Comma-separated list of column names from input-columns to exclude from processing.

key_columns
Comma-separated list of column names from input-columns that identify its data rows. These columns are included in the output table.

Examples

=> SELECT SVD ('svdmodel', 'small_svd', 'x1,x2,x3,x4');
SVD
--------------------------------------------------------------
Finished in 1 iterations.
Accepted Rows: 8  Rejected Rows: 0
(1 row)

=> CREATE TABLE transform_svd AS SELECT
     APPLY_SVD (id, x1, x2, x3, x4 USING PARAMETERS model_name='svdmodel', exclude_columns='id', key_columns='id')
     OVER () FROM small_svd;
CREATE TABLE

=> SELECT * FROM transform_svd;
id  |       col1        |        col2         |        col3         |        col4
----+-------------------+---------------------+---------------------+--------------------
4   |  0.44849499240202 |  -0.347260956311326 |   0.186958376368345 |  0.378561270493651
6   |  0.17652411036246 | -0.0753183783382909 |  -0.678196192333598 | 0.0567124770173372
1   | 0.494871802886819 |   0.161721379259287 |  0.0712816417153664 | -0.473145877877408
2   |  0.17652411036246 | -0.0753183783382909 |  -0.678196192333598 | 0.0567124770173372
3   | 0.150974762654569 |   0.589561842046029 | 0.00392654610109522 |  0.360011163271921
5   | 0.494871802886819 |   0.161721379259287 |  0.0712816417153664 | -0.473145877877408
8   |  0.44849499240202 |  -0.347260956311326 |   0.186958376368345 |  0.378561270493651
7   | 0.150974762654569 |   0.589561842046029 | 0.00392654610109522 |  0.360011163271921
(8 rows)

=> SELECT APPLY_INVERSE_SVD (* USING PARAMETERS model_name='svdmodel', exclude_columns='id',
key_columns='id') OVER () FROM transform_svd;
id  |        x1        |        x2        |        x3        |        x4
----+------------------+------------------+------------------+------------------
4 | 91.4056627665577 | 44.7629617207482 | 83.1704961993117 | 38.9274292265543
6 | 20.6468626294368 | 9.30974906868751 | 8.71006863405534 |  6.5855928603967
7 | 31.2494347777156 | 20.6336519003026 | 27.5668287751507 | 5.84427645886865
1 |  107.93376580719 | 51.6980548011917 | 97.9665796560552 | 40.4918236881051
2 | 20.6468626294368 | 9.30974906868751 | 8.71006863405534 |  6.5855928603967
3 | 31.2494347777156 | 20.6336519003026 | 27.5668287751507 | 5.84427645886865
5 |  107.93376580719 | 51.6980548011917 | 97.9665796560552 | 40.4918236881051
8 | 91.4056627665577 | 44.7629617207482 | 83.1704961993117 | 38.9274292265543
(8 rows)

See also