Dear R community,
    I am using a dataframe with lots of NAs and wish to create subsets from
that dataframe. In the example below I intend to create a subset with all
entries with V1>1. To my surprise the result also contains all entries with
V1=NA. I would wish to learn more why this is or what I do wrong. I know
that I can use the command "subset" and the NAs will not appear, but what is
"wrong" with a[a$V1>1,]?
Thank you!
Georg.
*******************
Georg Ehret
Johns Hopkins
Baltimore, USA


> a
            V1        V2          V3         V4         V5
1           NA        NA          NA -2056.5981  0.8472496
2           NA        NA          NA  1407.8786  1.3349255
3           NA        NA          NA   579.2203  0.6082337
4           NA        NA          NA  1337.0740  1.0346453
5           NA        NA   -3.732253  -246.7270  1.9218894
6           NA -4.111501  -50.372053 -1512.2618 -0.8425137
7  100.0000000 -2.343761 -132.606282   101.7575  1.1870040
8   -1.8899018 11.921323   15.988519 -1199.5994  0.1907434
9    0.4819706  5.677561   29.677330  -200.9182 -0.1213408
10  -1.4981107  6.224487  209.133480   188.8852 -1.3321220
> b<-a[a$V1>1,]
> b
      V1        V2        V3       V4       V5
NA    NA        NA        NA       NA       NA
NA.1  NA        NA        NA       NA       NA
NA.2  NA        NA        NA       NA       NA
NA.3  NA        NA        NA       NA       NA
NA.4  NA        NA        NA       NA       NA
NA.5  NA        NA        NA       NA       NA
7    100 -2.343761 -132.6063 101.7575 1.187004

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