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Li, Yan (IED)

2007-Aug-15 16:16 UTC

[R] Formula in lm inside lapply

I am trying to run separate regressions for different groups of
observations using the lapply function. It works fine when I write the
formula inside the lm() function. But I would like to pass formulae into
lm(), so I can do multiple models more easily. I got an error message
when I tried to do that. Here is my sample code:

#generating data
x1 <- rnorm(100,1)
x2 <- rnorm(100,1)
y  <- rnorm(100,1)
group <- rep(c("A","B"),c(40,60))
group <- factor(group)
df <- data.frame(y,x1,x2,group)

#write formula inside lm--works fine
res1 <- lapply(levels(df$group), function(x) lm(y~x1,df, subset = group
==x))
res1
res2 <- lapply(levels(df$group),function(x) lm(y~x1+x2,df, subset group ==x))
res2

#try to pass formula into lm()--does not work
formula1 <- as.formula(y~x1)
formula2 <- as.formula(y~x1+x2)
resf1 <- lapply(levels(df$group),function(x) lm(formula1,df, subset group
==x))
resf1
resf2 <- lapply(levels(df$group),function(x) lm(formula2,df, subset group
==x))
Resf2

The error message is 
'Error in eval(expr, envir, enclos): object "x" not found'

Any help is greatly appreciated!

Yan
--------------------------------------------------------

This is not an offer (or solicitation of an offer) to buy/se...{{dropped}}

Henrique Dallazuanna

2007-Aug-15 16:46 UTC

head link

[R] Formula in lm inside lapply

try this:

lapply(levels(df$group), function(x)lm(formula1, data=df[group==x,]))

-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

On 15/08/07, Li, Yan (IED) <Yan.Y.Li@morganstanley.com>
wrote:>
> I am trying to run separate regressions for different groups of
> observations using the lapply function. It works fine when I write the
> formula inside the lm() function. But I would like to pass formulae into
> lm(), so I can do multiple models more easily. I got an error message
> when I tried to do that. Here is my sample code:
>
> #generating data
> x1 <- rnorm(100,1)
> x2 <- rnorm(100,1)
> y  <- rnorm(100,1)
> group <- rep(c("A","B"),c(40,60))
> group <- factor(group)
> df <- data.frame(y,x1,x2,group)
>
> #write formula inside lm--works fine
> res1 <- lapply(levels(df$group), function(x) lm(y~x1,df, subset = group
> ==x))
> res1
> res2 <- lapply(levels(df$group),function(x) lm(y~x1+x2,df, subset >
group ==x))
> res2
>
> #try to pass formula into lm()--does not work
> formula1 <- as.formula(y~x1)
> formula2 <- as.formula(y~x1+x2)
> resf1 <- lapply(levels(df$group),function(x) lm(formula1,df, subset >
group ==x))
> resf1
> resf2 <- lapply(levels(df$group),function(x) lm(formula2,df, subset >
group ==x))
> Resf2
>
> The error message is
> 'Error in eval(expr, envir, enclos): object "x" not
found'
>
> Any help is greatly appreciated!
>
> Yan
> --------------------------------------------------------
>
> This is not an offer (or solicitation of an offer) to buy/se...{{dropped}}
>
> ______________________________________________
> 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.
>
	[[alternative HTML version deleted]]

Gabor Grothendieck

2007-Aug-15 16:53 UTC

head link

[R] Formula in lm inside lapply

It can't find x since the environment of formula1 and of formula2 is the
Global
Environment and x is not there -- its local to the function.

Try this:

#generating data
set.seed(1)
DF <- data.frame(y = rnorm(100, 1), x1 = rnorm(100, 1), x2 = rnorm(100, 1),
  group = rep(c("A", "B"), c(40, 60)))

formula1 <- as.formula(y ~ x1)
lapply(levels(DF$group), function(x) {
   environment(formula1) <- environment()
   lm(formula1, DF, subset = group == x)
})

formula2 <- as.formula(y ~ x1 + x2)
lapply(levels(DF$group), function(x) {
   environment(formula2) <- environment()
   lm(formula2, DF, subset = group == x)
})



On 8/15/07, Li, Yan (IED) <Yan.Y.Li at morganstanley.com>
wrote:> I am trying to run separate regressions for different groups of
> observations using the lapply function. It works fine when I write the
> formula inside the lm() function. But I would like to pass formulae into
> lm(), so I can do multiple models more easily. I got an error message
> when I tried to do that. Here is my sample code:
>
> #generating data
> x1 <- rnorm(100,1)
> x2 <- rnorm(100,1)
> y  <- rnorm(100,1)
> group <- rep(c("A","B"),c(40,60))
> group <- factor(group)
> df <- data.frame(y,x1,x2,group)
>
> #write formula inside lm--works fine
> res1 <- lapply(levels(df$group), function(x) lm(y~x1,df, subset = group
> ==x))
> res1
> res2 <- lapply(levels(df$group),function(x) lm(y~x1+x2,df, subset >
group ==x))
> res2
>
> #try to pass formula into lm()--does not work
> formula1 <- as.formula(y~x1)
> formula2 <- as.formula(y~x1+x2)
> resf1 <- lapply(levels(df$group),function(x) lm(formula1,df, subset >
group ==x))
> resf1
> resf2 <- lapply(levels(df$group),function(x) lm(formula2,df, subset >
group ==x))
> Resf2
>
> The error message is
> 'Error in eval(expr, envir, enclos): object "x" not
found'
>
> Any help is greatly appreciated!
>
> Yan
> --------------------------------------------------------
>
> This is not an offer (or solicitation of an offer) to buy/se...{{dropped}}
>
> ______________________________________________
> 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.
>

Weiwei Shi

2007-Aug-15 16:57 UTC

head link

[R] Formula in lm inside lapply

try this:
> x = predict(z, Iris[-train, ])
> x1 <- rnorm(100,1)
> x2 <- rnorm(100,1)
> y  <- rnorm(100,1)
> group <- rep(c("A","B"),c(40,60))
> group <- factor(group)
> df <- data.frame(y,x1,x2,group)
> resf1 <- lapply(levels(df$group),function(x) {formula1 <-
as.formula(y~x1); lm(formula1,df, subset =group ==x)}) # put the formula defn
into function(x)
> resf1[[1]]

Call:
lm(formula = formula1, data = df, subset = group == x)

Coefficients:
(Intercept)           x1
     0.8532       0.1189


[[2]]

Call:
lm(formula = formula1, data = df, subset = group == x)

Coefficients:
(Intercept)           x1
     0.7116       0.3398

HTH,

Weiwei

On 8/15/07, Li, Yan (IED) <Yan.Y.Li at morganstanley.com>
wrote:> I am trying to run separate regressions for different groups of
> observations using the lapply function. It works fine when I write the
> formula inside the lm() function. But I would like to pass formulae into
> lm(), so I can do multiple models more easily. I got an error message
> when I tried to do that. Here is my sample code:
>
> #generating data
> x1 <- rnorm(100,1)
> x2 <- rnorm(100,1)
> y  <- rnorm(100,1)
> group <- rep(c("A","B"),c(40,60))
> group <- factor(group)
> df <- data.frame(y,x1,x2,group)
>
> #write formula inside lm--works fine
> res1 <- lapply(levels(df$group), function(x) lm(y~x1,df, subset = group
> ==x))
> res1
> res2 <- lapply(levels(df$group),function(x) lm(y~x1+x2,df, subset >
group ==x))
> res2
>
> #try to pass formula into lm()--does not work
> formula1 <- as.formula(y~x1)
> formula2 <- as.formula(y~x1+x2)
> resf1 <- lapply(levels(df$group),function(x) lm(formula1,df, subset >
group ==x))
> resf1
> resf2 <- lapply(levels(df$group),function(x) lm(formula2,df, subset >
group ==x))
> Resf2
>
> The error message is
> 'Error in eval(expr, envir, enclos): object "x" not
found'
>
> Any help is greatly appreciated!
>
> Yan
> --------------------------------------------------------
>
> This is not an offer (or solicitation of an offer) to buy/se...{{dropped}}
>
> ______________________________________________
> 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.
>

-- 
Weiwei Shi, Ph.D
Research Scientist
GeneGO, Inc.

"Did you always know?"
"No, I did not. But I believed..."
---Matrix III

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