r subset(df, condition) 与 df$[condition, ] [duplicate] 不同的结果

Question

R中带有子集data.frame的一些有线输出。

这是我使用的文件

https://d37djvu3ytnwxt.cloudfront.net/assets/courseware/v1/ccdc87b80d92a9c24de2f04daec5bb58/asset-v1:MITx+15.071x+2T2017+type@asset+block/WHO.csv

在 R 中读取数据后，有 194 个 obs。有 13 个变量。

> str(WHO)
'data.frame':   194 obs. of  13 variables:
$ Country                      : Factor w/ 194 levels "Afghanistan",..: 1 2 3 4 5 6 7 8 9 10 ...
$ Region                       : Factor w/ 6 levels "Africa","Americas",..: 3 4 1 4 1 2 2 4 6 4 ...
$ Population                   : int  29825 3162 38482 78 20821 89 41087 2969 23050 8464 ...
$ Under15                      : num  47.4 21.3 27.4 15.2 47.6 ...
$ Over60                       : num  3.82 14.93 7.17 22.86 3.84 ...
$ FertilityRate                : num  5.4 1.75 2.83 NA 6.1 2.12 2.2 1.74 1.89 1.44 ...
$ LifeExpectancy               : int  60 74 73 82 51 75 76 71 82 81 ...
$ ChildMortality               : num  98.5 16.7 20 3.2 163.5 ...
$ CellularSubscribers          : num  54.3 96.4 99 75.5 48.4 ...
$ LiteracyRate                 : num  NA NA NA NA 70.1 99 97.8 99.6 NA NA ...
$ GNI                          : num  1140 8820 8310 NA 5230 ...
$ PrimarySchoolEnrollmentMale  : num  NA NA 98.2 78.4 93.1 91.1 NA NA 96.9 NA ...
$ PrimarySchoolEnrollmentFemale: num  NA NA 96.4 79.4 78.2 84.5 NA NA 97.5 NA ...

但使用函数subset进行子集化的结果与df[,]不同，如下例所示。

> Outliers <- WHO[WHO$GNI > 10000 & WHO$FertilityRate > 2.5,]
> nrow(Outliers)
  [1] 27
Country                Region Population Under15 Over60 FertilityRate LifeExpectancy ChildMortality CellularSubscribers
NA                 <NA>                  <NA>         NA      NA     NA            NA             NA             NA                  NA
23             Botswana                Africa       2004   33.75   5.63          2.71             66           53.3              142.82
NA.1               <NA>                  <NA>         NA      NA     NA            NA             NA             NA                  NA
NA.2               <NA>                  <NA>         NA      NA     NA            NA             NA             NA                  NA
(trimmed ...)

有很多 NA obs。

当使用 subset 函数时，产生正确的结果。

> Outliers <- subset(WHO, GNI > 10000 & FertilityRate > 2.5)
> nrow(Outliers)
[1] 7
> Outliers
          Country                Region Population Under15 Over60 FertilityRate LifeExpectancy ChildMortality CellularSubscribers
23           Botswana                Africa       2004   33.75   5.63          2.71             66           53.3              142.82
56  Equatorial Guinea                Africa        736   38.95   4.53          5.04             54          100.3               59.15
63              Gabon                Africa       1633   38.49   7.38          4.18             62           62.0              117.32
83             Israel                Europe       7644   27.53  15.15          2.92             82            4.2              121.66
88         Kazakhstan                Europe      16271   25.46  10.04          2.52             67           18.7              155.74
131            Panama              Americas       3802   28.65  10.13          2.52             77           18.5              188.60
150      Saudi Arabia Eastern Mediterranean      28288   29.69   4.59          2.76             76            8.6              191.24
(trimmed ...)

Answer 1

如何确保首先摆脱 NA？

Outliers <- WHO[!is.na(WHO$GNI) & WHO$GNI > 10000 & 
!is.na(WHO$FertilityRate) & WHO$FertilityRate > 2.5,]