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https://issues.apache.org/jira/browse/ARROW-18241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17629916#comment-17629916
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Neal Richardson commented on ARROW-18241:
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There are some string functions we could perhaps use to construct this, like
{{ascii_is_decimal}}, and do something like {{ifelse(ascii_is_decimal(x), x,
NA_character_)}} before doing the {{cast()}}.
> [C++] Add cast option to return null for values that can't convert
> ------------------------------------------------------------------
>
> Key: ARROW-18241
> URL: https://issues.apache.org/jira/browse/ARROW-18241
> Project: Apache Arrow
> Issue Type: Bug
> Components: C++, R
> Reporter: Lucas Mation
> Priority: Major
>
> I am importing a dataset with arrow, and then converting variable types. But
> I got an error message because the `arrow` implementation of `as.integer`
> can't handle empty strings (which is legal in base R). Is this a bug?
> {code:r}
> #In R
> '' %>% as.integer()
> [1] NA
>
> #in arrow
> q <- data.table(x=c('','1','2'))
> q %>% write_dataset('q')
> q2 <- 'q' %>% open_dataset %>% mutate(x=as.integer(x)) %>% collect
> Error in `collect()`:
> ! Invalid: Failed to parse string: '' as a scalar of type int32
> Run `rlang::last_error()` to see where the error occurred.
> {code}
> Update: tryed to preprocess x with `ifelse` but it also did not work.
> {code:r}
> 'q' %>% open_dataset %>% mutate(x= ifelse(x=='',NA,x)) %>%
> mutate(x=as.integer(x)) %>% collect
> Error in `collect()`:
> ! NotImplemented: Function 'if_else' has no kernel matching input types
> (bool, bool, string)
> Run `rlang::last_error()` to see where the error occurred.
> {code}
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