[R] Need help for loop code, thanks

[jim holtman]

you can use sqldf:

> dat = read.table(textConnection('V1    V2     v3
+
+  1      a       1.3
+  1      a       1.5
+  1      b       2.0
+  1      a       2.3
+  1      a       3.4
+  1      c       5.5
+  1      d       6.0
+  1      a       7.0
+  2      f        1.5
+  2      g        1.6
+  2      f         3.4
+  2      f         4.0
+  2      g        4.6
+  2      c        5.0
+
+  2      a        5.3'),header=TRUE)
> closeAllConnections()
> require(sqldf)
> sqldf("select V1, V2, max(V3) from dat group by V1, V2")
  V1 V2 max(V3)
1  1  a     7.0
2  1  b     2.0
3  1  c     5.5
4  1  d     6.0
5  2  a     5.3
6  2  c     5.0
7  2  f     4.0
8  2  g     4.6
>


On Thu, Oct 7, 2010 at 11:39 AM, wangguojie2006
<wangguojie2006 at gmail.com> wrote:
>
> Dear fellows,
>
> I've been working this problem for a day and still can't see where the
> problem is. I really appreciate if anyone can help me out.
>
> My data is like:
>
> V1    V2     v3
> 1      a       1.3
> 1      a       1.5
> 1      b       2.0
> 1      a       2.3
> 1      a       3.4
> 1      c       5.5
> 1      d       6.0
> 1      a       7.0
> 2      f        1.5
> 2      g        1.6
> 2      f         3.4
> 2      f         4.0
> 2      g        4.6
> 2      c        5.0
> 2      a        5.3
>
> What I want to do is to get the max value of V3 for each unique V2 in each
> V1. For example, when V1=1, unique V2 is (a, b, c, d), and corresponding max
> value of V3 is (7.0, 2.0, 5.5, 6.0). And V1=2, unique V2 is (f, g, c, a) and
> max value of V3 is (4.0, 4.6, 5.0, 5.3). Then combinne these max values.
>
> My code is like:
>
> z<-NULL
> x<-NULL;y<-NULL
> for (j in 1:2)
> {
>  x<-unique(V2[V1==j])
>   for (i in 1:length(x))
>    {
>     y[i]<-max(V3[V2==x[i] & V1==j])
>    }
>  z<-c(z,y)
> }
> length(z)
>
> My problem is the length of z is much bigger than the length of I'm supposed
> to get, like above data, I should only get 8 max values. But the code will
> return me a number bigger than 8. I'm thinking there might be some
> overlapping problem. Can someone help?
>
> Thank you for your time.
>
> Best,
>
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Need-help-for-loop-code-thanks-tp2967036p2967036.html
> Sent from the R help mailing list archive at Nabble.com.
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?