[R] Problems with lm()

Andrew Robinson
Thu, 19 Jun 2008 08:49:00 -0000

In your data, subject is nested within sequence.  Was that your
intention?

> a<-c(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14)
> b<-c(1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2)
> c<-c(2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2)
> d<-c(2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1)
>
e<-c(1739,1633,1481,1837,1780,2073,1374,1629,1555,1385,1756,1522,1566,1643,
+ 1939,1615,1475,1759,1388,1483,1127,1682,1542,1247,1235,1605,1598,1718
+ )
> Data<-data.frame(subject=as.factor(a),
+ drug=as.factor(b), period=as.factor(c),
+ sequence=as.factor(d), Max=e)
> Data
   subject drug period sequence  Max
1        1    1      2        2 1739
2        1    2      1        2 1633
3        2    1      1        1 1481
4        2    2      2        1 1837
5        3    1      2        2 1780
6        3    2      1        2 2073
7        4    1      1        1 1374
8        4    2      2        1 1629
9        5    1      2        2 1555
10       5    2      1        2 1385
11       6    1      1        1 1756
12       6    2      2        1 1522
13       7    1      2        2 1566
14       7    2      1        2 1643
15       8    1      1        1 1939
16       8    2      2        1 1615
17       9    1      2        2 1475
18       9    2      1        2 1759
19      10    1      1        1 1388
20      10    2      2        1 1483
21      11    1      2        2 1127
22      11    2      1        2 1682
23      12    1      1        1 1542
24      12    2      2        1 1247
25      13    1      2        2 1235
26      13    2      1        2 1605
27      14    1      1        1 1598
28      14    2      2        1 1718



Andrew


On Thu, Jun 19, 2008 at 04:29:16PM +0800, leeznar wrote:
> Dear R-users:
>
> I am a new R-user and I have a question about lm
> function.  Here is my data.
> a<-c(1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14)
> b<-c(1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2)
> c<-c(2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2)
> d<-c(2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1,2,2,1,1)
>
e<-c(1739,1633,1481,1837,1780,2073,1374,1629,1555,1385,1756,1522,1566,1643,1939,1615,1475,1759,1388,1483,1127,1682,1542,1247,1235,1605,1598,1718
> )
> Data<-data.frame(subject=as.factor(a),
> drug=as.factor(b), period=as.factor(c),
> sequence=as.factor(d), Max=e)
>
> lm3<- lm(Max ~subject*sequence + sequence + period +
> drug, data=Data)
> print(lm3)
> anova(lm3)
>
> When I use lm to fit the data, there are some problems
> in ??subject*sequence??.   I have use GLM in SPSS to
> fit the same data, and it seems there is no problem.
>
> I don??t know where my problem is.  How can I get the
> same result with SPSS? How can I do?
>
> Best regards,
> Hsin-Ya Lee
>
>
>
>
>
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--
Andrew Robinson
Department of Mathematics and Statistics            Tel: +61-3-8344-6410
University of Melbourne, VIC 3010 Australia         Fax: +61-3-8344-4599