Hi All,
I have a dataset which contains 4 variables: area, group, time, y,
Area is a factor that has two levels A and B, group is a factor that is
nested within area. There are four groups within each area.
y is the response variable, and time refers to different days.
Below is the how data looks like.
First, I fit separate ancova for each area (area A and B), For each area,
I obtained different regression lines for each group within that area.
mod1 <- lm(y ~ month * group, data=two[two$area=="A"]
mod2 <- lm(y ~ month * group, data=two[two$area=="B"]
I want to fit the model at one time by using the nested structure
mod3 <- lm(y ~ -1+ month * (area/group), data=two)
I get different results using mod 3 from using mod1 and mod2.
Can someone give some suggestion on this. How can I specify the model in
R to simultaneously fit the model to get the same results as from mod1 and
mod2.
Thanks very much!
Hanna
> head(two[two$area=="A",]) group time y area
79 1 3 -1.394327 A
80 1 6 -1.435485 A
81 1 9 -1.406497 A
82 1 12 -1.265848 A
83 1 0 -1.316768 A
84 1 6 -1.431292 A> head(two[two$area=="B",]) group time
y area
1 1 0 -2.145581 B
2 1 0 -1.910543 B
3 1 0 -2.128632 B
4 1 3 -2.079442 B
5 1 3 -2.273026 B
6 1 6 -2.312635 B
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Dear Hannah You say they are different (mod3 from mod1 and mod2) but in what way are the results different? On 12/03/2017 15:38, li li wrote:> Hi All, > I have a dataset which contains 4 variables: area, group, time, y, > Area is a factor that has two levels A and B, group is a factor that is > nested within area. There are four groups within each area. > y is the response variable, and time refers to different days. > > Below is the how data looks like. > > First, I fit separate ancova for each area (area A and B), For each area, > I obtained different regression lines for each group within that area. > > mod1 <- lm(y ~ month * group, data=two[two$area=="A"] > > mod2 <- lm(y ~ month * group, data=two[two$area=="B"] > > I want to fit the model at one time by using the nested structure > > mod3 <- lm(y ~ -1+ month * (area/group), data=two) > > I get different results using mod 3 from using mod1 and mod2. > > Can someone give some suggestion on this. How can I specify the model in > R to simultaneously fit the model to get the same results as from mod1 and > mod2. > > Thanks very much! > Hanna > >> head(two[two$area=="A",]) group time y area > 79 1 3 -1.394327 A > 80 1 6 -1.435485 A > 81 1 9 -1.406497 A > 82 1 12 -1.265848 A > 83 1 0 -1.316768 A > 84 1 6 -1.431292 A> head(two[two$area=="B",]) group time > y area > 1 1 0 -2.145581 B > 2 1 0 -1.910543 B > 3 1 0 -2.128632 B > 4 1 3 -2.079442 B > 5 1 3 -2.273026 B > 6 1 6 -2.312635 B > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. >-- Michael http://www.dewey.myzen.co.uk/home.html
I think you need either mod4 <- lm( y ~ -1 + area / (month*group), data=two) mod5 <- lm( y ~ area / (month*group), data=two) With either of those, area:month and area:group and Residuals add up. On Sun, Mar 12, 2017 at 10:39 li li <hannah.hlx at gmail.com> wrote:> Hi All, > I have a dataset which contains 4 variables: area, group, time, y, > Area is a factor that has two levels A and B, group is a factor that is > nested within area. There are four groups within each area. > y is the response variable, and time refers to different days. > > Below is the how data looks like. > > First, I fit separate ancova for each area (area A and B), For each area, > I obtained different regression lines for each group within that area. > > mod1 <- lm(y ~ month * group, data=two[two$area=="A"] > > mod2 <- lm(y ~ month * group, data=two[two$area=="B"] > > I want to fit the model at one time by using the nested structure > > mod3 <- lm(y ~ -1+ month * (area/group), data=two) > > I get different results using mod 3 from using mod1 and mod2. > > Can someone give some suggestion on this. How can I specify the model in > R to simultaneously fit the model to get the same results as from mod1 and > mod2. > > Thanks very much! > Hanna > > > head(two[two$area=="A",]) group time y area > 79 1 3 -1.394327 A > 80 1 6 -1.435485 A > 81 1 9 -1.406497 A > 82 1 12 -1.265848 A > 83 1 0 -1.316768 A > 84 1 6 -1.431292 A> head(two[two$area=="B",]) group time > y area > 1 1 0 -2.145581 B > 2 1 0 -1.910543 B > 3 1 0 -2.128632 B > 4 1 3 -2.079442 B > 5 1 3 -2.273026 B > 6 1 6 -2.312635 B > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. >[[alternative HTML version deleted]]
Thanks so much, Richard. That works. Hanna 2017-03-12 14:31 GMT-04:00 Richard M. Heiberger <rmh at temple.edu>:> I think you need either > > mod4 <- lm( y ~ -1 + area / (month*group), data=two) > > mod5 <- lm( y ~ area / (month*group), data=two) > > With either of those, area:month and area:group and Residuals add up. > > > On Sun, Mar 12, 2017 at 10:39 li li <hannah.hlx at gmail.com> wrote: > >> Hi All, >> I have a dataset which contains 4 variables: area, group, time, y, >> Area is a factor that has two levels A and B, group is a factor that is >> nested within area. There are four groups within each area. >> y is the response variable, and time refers to different days. >> >> Below is the how data looks like. >> >> First, I fit separate ancova for each area (area A and B), For each >> area, >> I obtained different regression lines for each group within that area. >> >> mod1 <- lm(y ~ month * group, data=two[two$area=="A"] >> >> mod2 <- lm(y ~ month * group, data=two[two$area=="B"] >> >> I want to fit the model at one time by using the nested structure >> >> mod3 <- lm(y ~ -1+ month * (area/group), data=two) >> >> I get different results using mod 3 from using mod1 and mod2. >> >> Can someone give some suggestion on this. How can I specify the model >> in >> R to simultaneously fit the model to get the same results as from mod1 and >> mod2. >> >> Thanks very much! >> Hanna >> >> > head(two[two$area=="A",]) group time y area >> 79 1 3 -1.394327 A >> 80 1 6 -1.435485 A >> 81 1 9 -1.406497 A >> 82 1 12 -1.265848 A >> 83 1 0 -1.316768 A >> 84 1 6 -1.431292 A> head(two[two$area=="B",]) group time >> y area >> 1 1 0 -2.145581 B >> 2 1 0 -1.910543 B >> 3 1 0 -2.128632 B >> 4 1 3 -2.079442 B >> 5 1 3 -2.273026 B >> 6 1 6 -2.312635 B >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> 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. >> >[[alternative HTML version deleted]]