NAME
Data::TableData::Lookup - Lookup value in a table data structure
VERSION
This document describes version 0.003 of Data::TableData::Lookup (from
Perl distribution Data-TableData-Lookup), released on 2022-05-06.
SYNOPSIS
use Data::TableData::Lookup qw(
table_vlookup
);
# exact matching
table_vlookup(
table => [
{min_income=> 0, tax_rate=>0.13},
{min_income=> 8_000, tax_rate=>0.18},
{min_income=> 15_000, tax_rate=>0.22},
{min_income=> 35_000, tax_rate=>0.30},
{min_income=> 85_000, tax_rate=>0.39},
{min_income=>140_000, tax_rate=>0.45},
],
lookup_field => 'min_income',
lookup_value => 35_000,
result_field => 'tax_rate',
); # => 0.30
# exact matching, not found
table_vlookup(
table => [
{min_income=> 0, tax_rate=>0.13},
{min_income=> 8_000, tax_rate=>0.18},
{min_income=> 15_000, tax_rate=>0.22},
{min_income=> 35_000, tax_rate=>0.30},
{min_income=> 85_000, tax_rate=>0.39},
{min_income=>140_000, tax_rate=>0.45},
],
lookup_field => 'min_income',
lookup_value => 40_000,
result_field => 'tax_rate',
); # => undef
# approximate matching
table_vlookup(
table => [
{min_income=> 0, tax_rate=>0.13},
{min_income=> 8_000, tax_rate=>0.18},
{min_income=> 15_000, tax_rate=>0.22},
{min_income=> 35_000, tax_rate=>0.30},
{min_income=> 85_000, tax_rate=>0.39},
{min_income=>140_000, tax_rate=>0.45},
],
lookup_field => 'min_income',
lookup_value => 40_000,
result_field => 'tax_rate',
approx => 1,
); # => 0.30
# approximate matching & interpolated result
table_vlookup(
table => [
{min_income=> 0, tax_rate=>0.13},
{min_income=> 8_000, tax_rate=>0.18},
{min_income=> 15_000, tax_rate=>0.22},
{min_income=> 35_000, tax_rate=>0.30},
{min_income=> 85_000, tax_rate=>0.39},
{min_income=>140_000, tax_rate=>0.45},
],
lookup_field => 'min_income',
lookup_value => 40_000,
result_field => 'tax_rate',
approx => 1,
interpolate => 1,
); # => 0.309
FUNCTIONS
table_vlookup
Usage:
table_vlookup(%args) -> any
Look up value in a table row by row.
This routine looks up value in a table row by row. It is similar to the
spreadsheet function VLOOKUP, hence the same name being used. It is
basically a glorified map()+grep() that returns a single value (or you
can also say it's a glorified map+List::Util::first()).
Given a table, which is either an array-of-arrayrefs (aoa) or
array-of-hashrefs (aoh), this routine will run through it row by row
until it finds the value that you want. Once found, the value will be
returned. Otherwise, undef is returned.
Exact matching
The table is expected to be sorted in ascending order by the lookup
field. You specify a lookup value, which will be looked up in the lookup
field. Once the value is found, the result field of the correspending
row is returned and lookup is completed. When the lookup field already
exceeds the lookup value, the routine also concludes that the value is
not found, and the lookup is completed.
Example:
table => [
{min_income=> 0, tax_rate=>0.13},
{min_income=> 8_000, tax_rate=>0.18},
{min_income=> 15_000, tax_rate=>0.22},
{min_income=> 35_000, tax_rate=>0.30},
{min_income=> 85_000, tax_rate=>0.39},
{min_income=>140_000, tax_rate=>0.45},
],
lookup_field => 'min_income',
lookup_value => 35_000,
result_field => 'tax_rate',
will result in:
0.304
while if the lookup_value is 40_000, undef will be returned since it is
not found in any row of the table.
Approximate matching
If "approx" option is set to true, once the lookup field in a row
exceeds the lookup value, the result field of the previous row will be
returned (if any). For example, if lookup value is 40_000 then 0.30 will
be returned (the row where "min_income" is 35_000) since the next row
has "min_income" of 85_000 which already exceeds 40_000.
Interpolation of result
If, additionally, "interpolate" option is also set to true in addition
to "approx" option being set to true, a linear interpolation will be
done when an exact match fails. In the previous example, when lookup
value is 40_000, 0.309 will be returned, which is calculated with:
0.3 + (40_000 - 35_000)/(85_000 - 35_000)*(0.39 - 0.30)
In the case of there is no next row after "min_income" of 35_000, 0.30
will still be returned.
This function is not exported by default, but exportable.
Arguments ('*' denotes required arguments):
* approx => *bool*
Whether to do an approximate instead of an exact match.
See example in the function description.
* interpolate => *bool*
Do a linear interpolation.
When this option is set to true, will do a linear interpolation of
result when an exact match is not found. This will only be performed
if "approx" is also set to true.
See example in the function description.
Currently, you cannot use "interpolate" with "lookup_code".
* lookup_code => *code*
Supply code to match a row.
Unless what you want to match is custom, you usually specify
"lookup_value" and "lookup_field" instead.
The code will be passed the row (which is an arrayref or a hashref)
and optionally the lookup value too as the second argument if the
lookup value is specified. It is expected to return either -1, 0, 1
like the Perl's "cmp" or "<=>" operator. -1 means the lookup field
is less than the lookup value, 0 means equal, and 1 means greater
than.
With "approx" option not set to true, lookup will succeed once 0 is
returned. With "approx" set to true, lookup will succeed once 0 or 1
is returned.
* lookup_field => *str*
Where to look up the lookup value in.
Either an integer array index (for aoaos table) or a string hash key
(for aohos table).
Instead of "lookup_value" and "lookup_field", you can also specify
"lookup_code" instead.
* lookup_value => *any*
The value that you want to look up in the lookup field.
Instead of "lookup_value" and "lookup_field", you can also specify
"lookup_code" instead.
* result_field* => *str*
Where to get the result from.
Either an integer array index (for aoa table) or a string hash key
(for aoh table).
* table* => *array*
Either an aoaos (array of aos's a.k.a. array-of-scalars) or aohos
(array of hos's a.k.a. hash of scalars), e.g.:
# aoaos
[ # col1, col2, col3
[1,2,3],
[4,5,6],
[7,8,9], ]
or:
# aohos
[ {col1=>1, col2=>2, col3=>3},
{col1=>4, col2=>5, col3=>6},
{col1=>7, col2=>8, col3=>9}, ]
Return value: (any)
HOMEPAGE
Please visit the project's homepage at
<https://metacpan.org/release/Data-TableData-Lookup>.
SOURCE
Source repository is at
<https://github.com/perlancar/perl-TableData-Lookup>.
SEE ALSO
AUTHOR
perlancar <perlancar@cpan.org>
CONTRIBUTING
To contribute, you can send patches by email/via RT, or send pull
requests on GitHub.
Most of the time, you don't need to build the distribution yourself. You
can simply modify the code, then test via:
% prove -l
If you want to build the distribution (e.g. to try to install it locally
on your system), you can install Dist::Zilla,
Dist::Zilla::PluginBundle::Author::PERLANCAR, and sometimes one or two
other Dist::Zilla plugin and/or Pod::Weaver::Plugin. Any additional
steps required beyond that are considered a bug and can be reported to
me.
COPYRIGHT AND LICENSE
This software is copyright (c) 2022, 2021 by perlancar
<perlancar@cpan.org>.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
BUGS
Please report any bugs or feature requests on the bugtracker website
<https://rt.cpan.org/Public/Dist/Display.html?Name=Data-TableData-Lookup
>
When submitting a bug or request, please include a test-file or a patch
to an existing test-file that illustrates the bug or desired feature.