R help - Oct 2006 - Rank Function

Does anyone know why the two rank functions gives
different results? I need to use the rank function in
a "for" loop, so the sequence to be ranked is given
values in the form of part (1). How can I use
assignment like in part (1) to get correct ranks as in
part (2)?

Thank You



Part (1)
i<-1.94
b<-0.95-i
c<-1.73-i
d<-2.62-i

y<-c(0.68,0.95,b,c,d)

y
0.68  0.95 -0.99 -0.21  0.68

rank(y)
3 5 1 2 4

Part(2)
rank(c(0.68,0.95,-0.99,-0.21,0.68))
3.5 5.0 1.0 2.0 3.5

> y<-round(c(0.68,0.95,b,c,d),2)
> rank(y)
[1] 3.5 5.0 1.0 2.0 3.5


On 10/10/06, Li Zhang <zhanglitt@yahoo.com> wrote:
>
> Does anyone know why the two rank functions gives
> different results? I need to use the rank function in
> a "for" loop, so the sequence to be ranked is given
> values in the form of part (1). How can I use
> assignment like in part (1) to get correct ranks as in
> part (2)?
>
> Thank You
>
>
>
> Part (1)
> i<-1.94
> b<-0.95-i
> c<-1.73-i
> d<-2.62-i
>
> y<-c(0.68,0.95,b,c,d)
>
> y
> 0.68  0.95 -0.99 -0.21  0.68
>
> rank(y)
> 3 5 1 2 4
>
> Part(2)
> rank(c(0.68,0.95,-0.99,-0.21,0.68))
> 3.5 5.0 1.0 2.0 3.5
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> 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.
>


-- 
================================David Barron
Said Business School
University of Oxford
Park End Street
Oxford OX1 1HP

	[[alternative HTML version deleted]]

Because y[1] and y[5] are not the same in Part1 but are in Part2:
> # using y from Part1
> y[5] - y[1]
[1] 1.110223e-16

You could round your numbers to 2 digits, say:
> rank(round(100*y)) # y is from Part1
[1] 3.5 5.0 1.0 2.0 3.5


On 10/10/06, Li Zhang <zhanglitt at yahoo.com>
wrote:
> Does anyone know why the two rank functions gives
> different results? I need to use the rank function in
> a "for" loop, so the sequence to be ranked is given
> values in the form of part (1). How can I use
> assignment like in part (1) to get correct ranks as in
> part (2)?
>
> Thank You
>
>
>
> Part (1)
> i<-1.94
> b<-0.95-i
> c<-1.73-i
> d<-2.62-i
>
> y<-c(0.68,0.95,b,c,d)
>
> y
> 0.68  0.95 -0.99 -0.21  0.68
>
> rank(y)
> 3 5 1 2 4
>
> Part(2)
> rank(c(0.68,0.95,-0.99,-0.21,0.68))
> 3.5 5.0 1.0 2.0 3.5
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> 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.
>

Li Zhang wrote:
> Does anyone know why the two rank functions gives
> different results? I need to use the rank function in
> a "for" loop, so the sequence to be ranked is given
> values in the form of part (1). How can I use
> assignment like in part (1) to get correct ranks as in
> part (2)?
> 
> Thank You
> 
> 
> 
> Part (1)
> i<-1.94
> b<-0.95-i
> c<-1.73-i
> d<-2.62-i
> 
> y<-c(0.68,0.95,b,c,d)
> 
> y
> 0.68  0.95 -0.99 -0.21  0.68
> 
> rank(y)
> 3 5 1 2 4
> 
> Part(2)
> rank(c(0.68,0.95,-0.99,-0.21,0.68))
> 3.5 5.0 1.0 2.0 3.5
> 
You have specified the exact numbers in part(2). Try part(1) with the 
following:

rank(zapsmall(y))

zapsmall removes tiny floating point errors that are not visible with 
the default representation of numbers.

Jim