### Contents

  * [Introduction](./_introduction.md)
  * [The Basic API](./basic_api.md)
  * [Batch Processing](././batch_processing.md)
  * [Configuration Options](./options.md)
  * [Row and Column Separators](./row_col_sep.md)
  * [Header Transformations](./header_transformations.md)
  * [Header Validations](./header_validations.md)
  * [**Data Transformations**](./data_transformations.md)
  * [Value Converters](./value_converters.md)
    
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# Data Transformations

SmarterCSV automatically transforms the values in each colum in order to normalize the data.
This behavior can be customized or disabled.

## Remove Empty Values
`remove_empty_values` is enabled by default
It removes any values which are `nil` or would be empty strings.

## Convert Values to Numeric
`convert_values_to_numeric` is enabled by default. 
SmarterCSV will convert strings containing Integers or Floats to the appropriate class.

Here is an example of using `convert_values_to_numeric` for numbers with leading zeros, e.g. ZIP codes:

```
  data = SmarterCSV.process('/tmp/zip.csv',  convert_values_to_numeric: { except: [:zip] })
   => [{:zip=>"00480"}, {:zip=>"51903"}, {:zip=>"12354"}, {:zip=>"02343"}]
```   

This will return the column `:zip` as a string with all digits intact.

## Remove Zero Values
`remove_zero_values` is disabled by default.
When enabled, it removes key/value pairs which have a numeric value equal to zero.

## Remove Values Matching
`remove_values_matching` is disabled by default. 
When enabled, this can help removing key/value pairs from result hashes which would cause problems. 

e.g.
 * `remove_values_matching: /^\$0\.0+$/` would remove $0.00 
 * `remove_values_matching: /^#VALUE!$/` would remove errors from Excel spreadsheets 

## Empty Hashes

It can happen that after all transformations, a row of the CSV file would produce a completely empty hash.

By default SmarterCSV uses `remove_empty_hashes: true` to remove these empty hashes from the result.

This can be set to `false`, to keep these empty hashes in the results.

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