R help - Feb 2008 - problem of subscript value from vector and list

Hi, everyone

I got some problems when trying to subscript the value of vector and 
list, by using calculated indices.
Here is the vector I am generated
lon<-rep(0,886);lat<-rep(0,691)
for (i in 1:886){
    lon[i]<-112+0.05*(i-1)
    }
for (i in 691:1){
    lat[i]<--44.5+0.05*(691-i)
    }
For a given location of lon(xp) and lat(yp), I would like to calculate 
the  position of them, and using that to get the value for the location 
from one list.
xp<-c(112,112.05); yp<-c(-10,-10.10)

x<-rep(0,length(xp)); y<-rep(0,length(yp))
for (i in 1:length(xp)){
    x[i]<-(xp[i]-112)/0.05+1
    }
for(j in 1:length(yp)){
    y[j]<-(-10-yp[j])/0.05+1
    }
So here the value of x and y should indicate the position where xp and 
yp are in the vector lon and lat.  And it appears to be the right 
number.  But when I tried to retrieve the value of lon using the 
position, it returns the wrong value.  Here's the result I got
 > x
[1] 1 2
 > lon[x]
[1] 112 112
 > lon[c(1,2)]
[1] 112.00 112.05
 > y
[1] 1 3
 > lat[y]
[1] -10.00 -10.05
 > lat[c(1,3)]
[1] -10.0 -10.1

I have no idea why it returns the wrong value when I subscripts by x, 
while it works perfectly fine when I subscripts with the value of x 
directly.  Is there any special rule of subscripts?  My version of R is 
2.5.1.
Thanks a lot

Jingru Dai
 ----
 School of Mathematical Sciences
 Rm 454, Building 28
 Monash University, 3800
 Victoria, Australia

I think you are getting a rounding or truncating
problem in the printing 

Try print[lon[x]) 

and see what you get
--- Jingru Dai <jingru.dai at sci.monash.edu.au> wrote:
> Hi, everyone
> 
> I got some problems when trying to subscript the
> value of vector and 
> list, by using calculated indices.
> Here is the vector I am generated
> lon<-rep(0,886);lat<-rep(0,691)
> for (i in 1:886){
>     lon[i]<-112+0.05*(i-1)
>     }
> for (i in 691:1){
>     lat[i]<--44.5+0.05*(691-i)
>     }
> For a given location of lon(xp) and lat(yp), I would
> like to calculate 
> the  position of them, and using that to get the
> value for the location 
> from one list.
> xp<-c(112,112.05); yp<-c(-10,-10.10)
> 
> x<-rep(0,length(xp)); y<-rep(0,length(yp))
> for (i in 1:length(xp)){
>     x[i]<-(xp[i]-112)/0.05+1
>     }
> for(j in 1:length(yp)){
>     y[j]<-(-10-yp[j])/0.05+1
>     }
> So here the value of x and y should indicate the
> position where xp and 
> yp are in the vector lon and lat.  And it appears to
> be the right 
> number.  But when I tried to retrieve the value of
> lon using the 
> position, it returns the wrong value.  Here's the
> result I got
>  > x
> [1] 1 2
>  > lon[x]
> [1] 112 112
>  > lon[c(1,2)]
> [1] 112.00 112.05
>  > y
> [1] 1 3
>  > lat[y]
> [1] -10.00 -10.05
>  > lat[c(1,3)]
> [1] -10.0 -10.1
> 
> I have no idea why it returns the wrong value when I
> subscripts by x, 
> while it works perfectly fine when I subscripts with
> the value of x 
> directly.  Is there any special rule of subscripts? 
> My version of R is 
> 2.5.1.
> Thanks a lot
> 
> Jingru Dai
>  ----
>  School of Mathematical Sciences
>  Rm 454, Building 28
>  Monash University, 3800
>  Victoria, Australia
> 
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