[GitHub] [arrow] nealrichardson commented on issue #7385: bad handling of Int64 column of dataframe when reading in R with read_feather

[GitBox <gi...@apache.org>]

nealrichardson commented on issue #7385:
URL: https://github.com/apache/arrow/issues/7385#issuecomment-641472127


   This appears to be a feature of how `data.matrix()` interacts with `bit64::integer64` class objects. Here's a reprex without involving `arrow`:
   
   ```
   > df <- data.frame(a=bit64::as.integer64(1:2), b=bit64::as.integer64(3:4))
   > df
     a b
   1 1 3
   2 2 4
   > data.matrix(df)
                    a             b
   [1,] 4.940656e-324 1.482197e-323
   [2,] 9.881313e-324 1.976263e-323
   ```
   
   You could fix this in your example either by providing a schema in Python with int32 types, or by calling `as.integer` on the columns of your data.frame before calling `data.matrix()`.
   
   One could argue that we should downcast int64 to int32 if there are no out of bounds values since that's what R can natively handle. I made https://issues.apache.org/jira/browse/ARROW-9083 to consider that.


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