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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2020/12/27 19:56:09 UTC
[GitHub] [arrow] bu2 opened a new pull request #9022: Add replace and isnan scalar kernels
bu2 opened a new pull request #9022:
URL: https://github.com/apache/arrow/pull/9022
Purpose a "replace" compute kernel which could fulfil ARROW-10641 - [C++] A "replace" or "map" kernel to replace values in array based on mapping (@jorisvandenbossche). The implementation is inspired by "fill_null" kernel except it takes an additional BooleanArray parameter which is used as a mask to trigger value replacement.
**WARNING:** the current implementation expects all null values to be replaced in the output (corresponding bit set to 1 in input mask) because it will not carry nulls into the output (feel free to share your thoughts on the current implementation and to give me hints on the easiest way to deal with nulls that should make it in the output).
Add a "is_nan" kernel to check for NaN "equality" for FloatArray and DoubleArray (based on std::isnan()). The kernel signature is based on "is_null" kernel so I put my code in arrow/compute/kernels/scalar_validity.cc... but the implementation take some inspiration from "compare" kernel.
Both kernels are used to mimic pandas.DataFrame.fillna(value=X) in C++. See below an example of usage:
`
template <typename value_type>
std::shared_ptr<DataFrame> DataFrame::fillna(value_type value) {
auto outdf = std::make_shared<DataFrame>();
if (outdf->table_->num_rows() == 0)
outdf->table_ = arrow::Table::Make(
std::make_shared<arrow::Schema>(std::vector<std::shared_ptr<arrow::Field>>()),
std::vector<std::shared_ptr<arrow::ChunkedArray>>(),
this->table_->num_rows());
for (int i = 0 ; i < this->table_->num_columns() ; ++i) {
if (this->table_->ColumnNames()[i] == INDEX_COLUMN) {
auto field = this->table_->schema()->field(i);
auto chunked_array = this->table_->column(i);
outdf->table_ = outdf->table_->AddColumn(i, field, chunked_array).ValueOrDie();
} else {
auto field = this->table_->schema()->field(i);
auto chunked_array = this->table_->column(i);
auto value_datum = arrow::compute::Cast(arrow::Datum(value), chunked_array->type()).ValueOrDie();
auto nulls = arrow::compute::IsNull(chunked_array).ValueOrDie();
auto nans = **arrow::compute::IsNan(chunked_array)**.ValueOrDie().chunked_array();
auto to_replace = arrow::compute::Or(nulls, nans).ValueOrDie();
auto clean_chunked_array = **arrow::compute::Replace(chunked_array, nans, value_datum)**.ValueOrDie().chunked_array();
outdf->table_ = outdf->table_->AddColumn(i, field, clean_chunked_array).ValueOrDie();
}
}
return outdf;
}
`
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[GitHub] [arrow] bu2 commented on pull request #9022: [C++] Add replace and isnan scalar kernels
Posted by GitBox <gi...@apache.org>.
bu2 commented on pull request #9022:
URL: https://github.com/apache/arrow/pull/9022#issuecomment-751533238
Killing this pull request to recreate 2 distinct pull requests (one for each kernel) with corresponding Jira ticket.
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[GitHub] [arrow] github-actions[bot] commented on pull request #9022: [C++] Add replace and isnan scalar kernels
Posted by GitBox <gi...@apache.org>.
github-actions[bot] commented on pull request #9022:
URL: https://github.com/apache/arrow/pull/9022#issuecomment-751510556
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Thanks for opening a pull request!
Could you open an issue for this pull request on JIRA?
https://issues.apache.org/jira/browse/ARROW
Then could you also rename pull request title in the following format?
ARROW-${JIRA_ID}: [${COMPONENT}] ${SUMMARY}
See also:
* [Other pull requests](https://github.com/apache/arrow/pulls/)
* [Contribution Guidelines - How to contribute patches](https://arrow.apache.org/docs/developers/contributing.html#how-to-contribute-patches)
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[GitHub] [arrow] bu2 closed pull request #9022: [C++] Add replace and isnan scalar kernels
Posted by GitBox <gi...@apache.org>.
bu2 closed pull request #9022:
URL: https://github.com/apache/arrow/pull/9022
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