::: {.cell hash='02_R_introduction_cache/pdf/unnamed-chunk-40_3ed0a1cc3b18759c955076e6f208dad3'}
::: {.cell-output .cell-output-stderr}
```
Warning in sqrt(-1): NaNs produced
```
:::

::: {.cell-output .cell-output-stdout}
```
[1] NaN
```
:::
:::