Matti Viljamaa
2016-Sep-09 12:11 UTC
[R] Comparison conditionals when extracting from data.frame not working reliably
I?m getting strange behaviour when trying to extract rows from a two-column
data.frame with double values.
My data looks like:
mom_iq kid_score
1 121.11750 65
2 89.36188 98
3 115.44320 85
4 99.44964 83
?
and I?m testing extracting rows that have mom_iq at some interval, so e.g.
kidmomiq[kidmomiq$mom_iq > 80.0 && kidmomiq$mom_iq < 130.0,]
correctly returns rows that have mom_iq \in ]80.0, 130.0[.
However, if I adjust this to:
kidmomiq[kidmomiq$mom_iq > 80.0 && kidmomiq$mom_iq < 120.0,]
(and there are clearly values that also fall \in ]80.0, 120.0[ !)
I get:
[1] mom_iq kid_score
<0 rows> (or 0-length row.names)
Why does the extraction fail on some values, but not some others?
Ista Zahn
2016-Sep-09 12:27 UTC
[R] Comparison conditionals when extracting from data.frame not working reliably
Use & instead of && --Ista On Sep 9, 2016 8:12 AM, "Matti Viljamaa" <mviljamaa at kapsi.fi> wrote:> I?m getting strange behaviour when trying to extract rows from a > two-column data.frame with double values. > > My data looks like: > > mom_iq kid_score > 1 121.11750 65 > 2 89.36188 98 > 3 115.44320 85 > 4 99.44964 83 > ? > > and I?m testing extracting rows that have mom_iq at some interval, so e.g. > > kidmomiq[kidmomiq$mom_iq > 80.0 && kidmomiq$mom_iq < 130.0,] > > correctly returns rows that have mom_iq \in ]80.0, 130.0[. > > However, if I adjust this to: > > kidmomiq[kidmomiq$mom_iq > 80.0 && kidmomiq$mom_iq < 120.0,] > > (and there are clearly values that also fall \in ]80.0, 120.0[ !) > > I get: > > [1] mom_iq kid_score > <0 rows> (or 0-length row.names) > > Why does the extraction fail on some values, but not some others? > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/ > posting-guide.html > and provide commented, minimal, self-contained, reproducible code.[[alternative HTML version deleted]]