Using rank() with subset [closed] - r

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I got this data here:
State Abb Region Change
3 Arizona AZ West 24.6
6 Colorado CO West 16.9
10 Florida FL South 17.6
11 Georgia GA South 18.3
13 Idaho ID West 21.1
29 Nevada NV West 35.1
34 North Carolina NC South 18.5
41 South Carolina SC South 15.3
44 Texas TX South 20.6
45 Utah UT West 23.8
I'm trying to extract a subset where Change > 40.
When I use
subset(uspopchange, rank(Change)>40)
it works
but when I use
subset(uspopchange, Change > 40)
it comes up with nothing.
Furthermore, if I use
subset(uspopchange, Change > 16.9)
it works also.
Why does it do that? Why do I need to user rank() to get my subset?
BTW: the data is from
install.packages("gcookbook")

Answer 1

> library(gcookbook)
> data(uspopchange)
> head(uspopchange[order(uspopchange$Change,decreasing=TRUE),])
State Abb Region Change
29 Nevada NV West 35.1
3 Arizona AZ West 24.6
45 Utah UT West 23.8
13 Idaho ID West 21.1
44 Texas TX South 20.6
34 North Carolina NC South 18.5
There are no rows with Change greater than 40. When you are using rank(Change) > 40 in your subset(), it is giving you the rows that, based on the value of Change, have a rank higher than 40. Since there are 50 rows in your data (Change has a length of 50), you are getting the rows that rank 41, 42, 43, ... , 50.
> Top10 <- subset(uspopchange, rank(Change)>40)
> Top10[order(Top10$Change,decreasing=TRUE),]
State Abb Region Change
29 Nevada NV West 35.1
3 Arizona AZ West 24.6
45 Utah UT West 23.8
13 Idaho ID West 21.1
44 Texas TX South 20.6
34 North Carolina NC South 18.5
11 Georgia GA South 18.3
10 Florida FL South 17.6
6 Colorado CO West 16.9
41 South Carolina SC South 15.3
##
> uspopchange[order(uspopchange$Change,decreasing=TRUE),][1:10,]
State Abb Region Change
29 Nevada NV West 35.1
3 Arizona AZ West 24.6
45 Utah UT West 23.8
13 Idaho ID West 21.1
44 Texas TX South 20.6
34 North Carolina NC South 18.5
11 Georgia GA South 18.3
10 Florida FL South 17.6
6 Colorado CO West 16.9
41 South Carolina SC South 15.3
Those are equivalent.