Tablesaw seriliaze null String values

[yelizgungor]

While serializing the tablesaw structure to a CSV string, I used CsvWriter and noticed that the default nullValue is being used as an empty string. To set a specific string, such as "__null_rep" or "__na_rep", I need to set the nullValue parameter with CsvWriteOptions. This is similar to the na_rep parameter used in the Python Pandas DataFrame to_csv method for serialization.

Table table = createNewTable();
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
CsvWriteOptions options = CsvWriteOptions.builder(byteArrayOutputStream)
            .header(true)
            .build();
 new CsvWriter().write(table, options)
 return byteArrayOutputStream.toByteArray();

[frankwondon]

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[lwhite1]

you can change the value before writing using one of the set methods defined on the column

…

On Thu, Jul 6, 2023 at 1:21 PM frankwondon ***@***.***> wrote: 这是来自QQ邮箱的假期自动回复邮件。你好，我最近正在休假中，无法亲自回复你的邮件。我将在假期结束后，尽快给你回复。 — Reply to this email directly, view it on GitHub <#1221 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA2FPAUZ5A7EDYUOEZ4RHJTXO3XYDANCNFSM6AAAAAA2AXOBPU> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[yelizgungor]

Yup, I will do that as you suggest in this issue. But it would be good to have a setting for that.
Thanks for response, @lwhite1

[lwhite1]

actually there is a setting, you can elect when writing to use a PrintFormatter (I forget the exact class name). You should be able to set a value for null there.

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On Thu, Jul 6, 2023 at 2:38 PM yelizgungor ***@***.***> wrote: Yup, I will do that as you suggest in this issue <#564>. But it would be good to have a setting for that. Thanks for response, @lwhite1 <https://github.com/lwhite1> — Reply to this email directly, view it on GitHub <#1221 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA2FPASH3POBLKJZJHRGVULXO4A3NANCNFSM6AAAAAA2AXOBPU> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[yelizgungor]

I updated the StringColumns formatter. But it seems CsvWriter calls getUnformattedString instead getString

[yelizgungor]

But AFAIS there is another main problem: There is no differentiation for StringColumn between an empty string and a null value to define if it isMissing

[lwhite1]

In tablesaw an empty string is a null value is a missing value.

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On Thu, Jul 6, 2023 at 6:25 PM yelizgungor ***@***.***> wrote: But AFAIS there is another main problem: There is no differentiation for StringColumn between an empty string and a null value to define if it isMissing <https://github.com/jtablesaw/tablesaw/blob/e11ef19d035c409367a2a05d6a8301188edf9387/core/src/main/java/tech/tablesaw/columns/AbstractColumnParser.java#L36-L41> — Reply to this email directly, view it on GitHub <#1221 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA2FPAWS3JONNG4F3VACVXDXO43MFANCNFSM6AAAAAA2AXOBPU> . You are receiving this because you were mentioned.Message ID: ***@***.***>