[jira] [Created] (ARROW-14125) [R] Why does round with arithmetic error?

["Jonathan Keane (Jira)" <ji...@apache.org>]

Jonathan Keane created ARROW-14125:
--------------------------------------

             Summary: [R] Why does round with arithmetic error?
                 Key: ARROW-14125
                 URL: https://issues.apache.org/jira/browse/ARROW-14125
             Project: Apache Arrow
          Issue Type: Bug
            Reporter: Jonathan Keane


Trying to call {{round}} with an arithmetic expression errors / pulls data into R:  

{code}
> library(arrow)
> library(dplyr)
> 
> df <- tibble(x = c(-1, -0.55, -0.5, -0.1, 0, 0.1, 0.5, 0.55, 1, NA, NaN))
> 
> # Round with arith inside pulls into R
> Table$create(df) %>% 
+   mutate(
+      r = round(x + 1)
+    ) %>%
+    collect()
Warning: Expression round(x + 1) not supported in Arrow; pulling data into R
# A tibble: 11 × 2
        x     r
    <dbl> <dbl>
 1  -1        0
 2  -0.55     0
 3  -0.5      0
 4  -0.1      1
 5   0        1
 6   0.1      1
 7   0.5      2
 8   0.55     2
 9   1        2
10  NA       NA
11 NaN      NaN
> 
> Table$create(df) %>% 
+   mutate(
+     r = round(0.00001 + 1)
+   ) %>%
+   collect()
Warning: Expression round(1e-05 + 1) not supported in Arrow; pulling data into R
# A tibble: 11 × 2
        x     r
    <dbl> <dbl>
 1  -1        1
 2  -0.55     1
 3  -0.5      1
 4  -0.1      1
 5   0        1
 6   0.1      1
 7   0.5      1
 8   0.55     1
 9   1        1
10  NA        1
11 NaN        1
{code}


However truncate works just fine:
{code}
> Table$create(df) %>% 
+   mutate(
+     r = trunc(0.00001 + 1)
+   ) %>%
+   collect()
# A tibble: 11 × 2
        x     r
    <dbl> <dbl>
 1  -1        1
 2  -0.55     1
 3  -0.5      1
 4  -0.1      1
 5   0        1
 6   0.1      1
 7   0.5      1
 8   0.55     1
 9   1        1
10  NA        1
11 NaN        1
> 
> 
> Table$create(df) %>% 
+   mutate(
+     r = trunc(x + 1)
+   ) %>%  collect()
# A tibble: 11 × 2
        x     r
    <dbl> <dbl>
 1  -1        0
 2  -0.55     0
 3  -0.5      0
 4  -0.1      0
 5   0        1
 6   0.1      1
 7   0.5      1
 8   0.55     1
 9   1        2
10  NA       NA
11 NaN      NaN
> 
{code}



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