Obtaining values of estimates from a regression; How do I get values from a list?

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Obtaining values of estimates from a regression; How do I get values from a list?

Sorkin, John
I am trying to obtain the coefficients from a regression (performed using lm).  I would like to get the value for the slope (i.e. estimate) for pre from the following regression:


fitchange <- lm(post-pre~pre,data=mydata2)


I have tried the following without any success:


zz <- summary(fitchange)["coefficients"]
class(zz)
print(zz)
zz[[2,1]]
zz[2,1]
zz["pre","Estimate"]


I clearly don't know how to select elements from the list returned by the summary function.


A reproducible version of my code follows:


mydata2 <-structure(list(pre = c(71.3302299440613, 86.2703384845455, 120.941698468568,
                              80.9020778388552, 84.9927752038908, 77.9108032451793, 111.007107108483,
                              93.288442414475, 126.097826796255, 111.63734644637),
                         post = c(45.9294556667686,
                                114.661937978585, 138.501558726477, 55.355775963925, 97.7906200355594,
                                71.1008233796004, 149.308274695789, 122.828428213951, 143.690814568562,
                                116.607579975539)), class = "data.frame", row.names = c(NA, -10L))

fitchange <- lm(post-pre~pre,data=mydata2)
zz <- summary(fitchange)["coefficients"]
class(zz)
print(zz)
zz[[2,1]]
zz[2,1]
zz["pre","Estimate"]


Any help you can offer would be appreciated.






John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)


        [[alternative HTML version deleted]]

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Re: Obtaining values of estimates from a regression; How do I get values from a list?

Eric Berger
You have some choices

fitchange$coefficients[2]

zz$coefficients[2,1]

Note that class(zz$coefficients) shows that it is a matrix.

HTH,
Eric


On Fri, Feb 22, 2019 at 9:45 AM Sorkin, John <[hidden email]>
wrote:

> I am trying to obtain the coefficients from a regression (performed using
> lm).  I would like to get the value for the slope (i.e. estimate) for pre
> from the following regression:
>
>
> fitchange <- lm(post-pre~pre,data=mydata2)
>
>
> I have tried the following without any success:
>
>
> zz <- summary(fitchange)["coefficients"]
> class(zz)
> print(zz)
> zz[[2,1]]
> zz[2,1]
> zz["pre","Estimate"]
>
>
> I clearly don't know how to select elements from the list returned by the
> summary function.
>
>
> A reproducible version of my code follows:
>
>
> mydata2 <-structure(list(pre = c(71.3302299440613, 86.2703384845455,
> 120.941698468568,
>                               80.9020778388552, 84.9927752038908,
> 77.9108032451793, 111.007107108483,
>                               93.288442414475, 126.097826796255,
> 111.63734644637),
>                          post = c(45.9294556667686,
>                                 114.661937978585, 138.501558726477,
> 55.355775963925, 97.7906200355594,
>                                 71.1008233796004, 149.308274695789,
> 122.828428213951, 143.690814568562,
>                                 116.607579975539)), class = "data.frame",
> row.names = c(NA, -10L))
>
> fitchange <- lm(post-pre~pre,data=mydata2)
> zz <- summary(fitchange)["coefficients"]
> class(zz)
> print(zz)
> zz[[2,1]]
> zz[2,1]
> zz["pre","Estimate"]
>
>
> Any help you can offer would be appreciated.
>
>
>
>
>
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and
> Geriatric Medicine
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] 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]]

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
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Re: Obtaining values of estimates from a regression; How do I get values from a list?

Ivan Calandra-5
I find that the str() function is really helpful to understand how an object is
structured, and therefore how to extract part(s) of it.

Try for example:
str(zz)
and it might help you understand why zz$coefficients[2,1] is what you were
looking for.

HTH
Ivan

--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49 (0) 2631 9772-243
https://www.researchgate.net/profile/Ivan_Calandra

On February 22, 2019 at 8:50 AM Eric Berger <[hidden email]> wrote:

> You have some choices
>
> fitchange$coefficients[2]
>
> zz$coefficients[2,1]
>
> Note that class(zz$coefficients) shows that it is a matrix.
>
> HTH,
> Eric
>
>
> On Fri, Feb 22, 2019 at 9:45 AM Sorkin, John <[hidden email]>
> wrote:
>
> > I am trying to obtain the coefficients from a regression (performed using
> > lm). I would like to get the value for the slope (i.e. estimate) for pre
> > from the following regression:
> >
> >
> > fitchange <- lm(post-pre~pre,data=mydata2)
> >
> >
> > I have tried the following without any success:
> >
> >
> > zz <- summary(fitchange)["coefficients"]
> > class(zz)
> > print(zz)
> > zz[[2,1]]
> > zz[2,1]
> > zz["pre","Estimate"]
> >
> >
> > I clearly don't know how to select elements from the list returned by the
> > summary function.
> >
> >
> > A reproducible version of my code follows:
> >
> >
> > mydata2 <-structure(list(pre = c(71.3302299440613, 86.2703384845455,
> > 120.941698468568,
> > 80.9020778388552, 84.9927752038908,
> > 77.9108032451793, 111.007107108483,
> > 93.288442414475, 126.097826796255,
> > 111.63734644637),
> > post = c(45.9294556667686,
> > 114.661937978585, 138.501558726477,
> > 55.355775963925, 97.7906200355594,
> > 71.1008233796004, 149.308274695789,
> > 122.828428213951, 143.690814568562,
> > 116.607579975539)), class = "data.frame",
> > row.names = c(NA, -10L))
> >
> > fitchange <- lm(post-pre~pre,data=mydata2)
> > zz <- summary(fitchange)["coefficients"]
> > class(zz)
> > print(zz)
> > zz[[2,1]]
> > zz[2,1]
> > zz["pre","Estimate"]
> >
> >
> > Any help you can offer would be appreciated.
> >
> >
> >
> >
> >
> >
> > John David Sorkin M.D., Ph.D.
> > Professor of Medicine
> > Chief, Biostatistics and Informatics
> > University of Maryland School of Medicine Division of Gerontology and
> > Geriatric Medicine
> > Baltimore VA Medical Center
> > 10 North Greene Street
> > GRECC (BT/18/GR)
> > Baltimore, MD 21201-1524
> > (Phone) 410-605-7119
> > (Fax) 410-605-7913 (Please call phone number above prior to faxing)
> >
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > [hidden email] 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]]
>
> ______________________________________________
> [hidden email] 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]]

______________________________________________
[hidden email] 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.
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Re: Obtaining values of estimates from a regression; How do I get values from a list?

Sorkin, John
Problem solved:

summary(fitchange)$coefficients[2,1]



John David Sorkin M.D., Ph.D.
Professor of Medicine
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)


________________________________
From: R-help <[hidden email]> on behalf of Ivan Calandra <[hidden email]>
Sent: Friday, February 22, 2019 2:58:47 AM
To: [hidden email]
Subject: Re: [R] Obtaining values of estimates from a regression; How do I get values from a list?

I find that the str() function is really helpful to understand how an object is
structured, and therefore how to extract part(s) of it.

Try for example:
str(zz)
and it might help you understand why zz$coefficients[2,1] is what you were
looking for.

HTH
Ivan

--
Dr. Ivan Calandra
TraCEr, laboratory for Traceology and Controlled Experiments
MONREPOS Archaeological Research Centre and
Museum for Human Behavioural Evolution
Schloss Monrepos
56567 Neuwied, Germany
+49 (0) 2631 9772-243
https://www.researchgate.net/profile/Ivan_Calandra

On February 22, 2019 at 8:50 AM Eric Berger <[hidden email]> wrote:

> You have some choices
>
> fitchange$coefficients[2]
>
> zz$coefficients[2,1]
>
> Note that class(zz$coefficients) shows that it is a matrix.
>
> HTH,
> Eric
>
>
> On Fri, Feb 22, 2019 at 9:45 AM Sorkin, John <[hidden email]>
> wrote:
>
> > I am trying to obtain the coefficients from a regression (performed using
> > lm). I would like to get the value for the slope (i.e. estimate) for pre
> > from the following regression:
> >
> >
> > fitchange <- lm(post-pre~pre,data=mydata2)
> >
> >
> > I have tried the following without any success:
> >
> >
> > zz <- summary(fitchange)["coefficients"]
> > class(zz)
> > print(zz)
> > zz[[2,1]]
> > zz[2,1]
> > zz["pre","Estimate"]
> >
> >
> > I clearly don't know how to select elements from the list returned by the
> > summary function.
> >
> >
> > A reproducible version of my code follows:
> >
> >
> > mydata2 <-structure(list(pre = c(71.3302299440613, 86.2703384845455,
> > 120.941698468568,
> > 80.9020778388552, 84.9927752038908,
> > 77.9108032451793, 111.007107108483,
> > 93.288442414475, 126.097826796255,
> > 111.63734644637),
> > post = c(45.9294556667686,
> > 114.661937978585, 138.501558726477,
> > 55.355775963925, 97.7906200355594,
> > 71.1008233796004, 149.308274695789,
> > 122.828428213951, 143.690814568562,
> > 116.607579975539)), class = "data.frame",
> > row.names = c(NA, -10L))
> >
> > fitchange <- lm(post-pre~pre,data=mydata2)
> > zz <- summary(fitchange)["coefficients"]
> > class(zz)
> > print(zz)
> > zz[[2,1]]
> > zz[2,1]
> > zz["pre","Estimate"]
> >
> >
> > Any help you can offer would be appreciated.
> >
> >
> >
> >
> >
> >
> > John David Sorkin M.D., Ph.D.
> > Professor of Medicine
> > Chief, Biostatistics and Informatics
> > University of Maryland School of Medicine Division of Gerontology and
> > Geriatric Medicine
> > Baltimore VA Medical Center
> > 10 North Greene Street
> > GRECC (BT/18/GR)
> > Baltimore, MD 21201-1524
> > (Phone) 410-605-7119
> > (Fax) 410-605-7913 (Please call phone number above prior to faxing)
> >
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > [hidden email] 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]]
>
> ______________________________________________
> [hidden email] 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]]

______________________________________________
[hidden email] 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]]

______________________________________________
[hidden email] 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.
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Re: Obtaining values of estimates from a regression; How do I get values from a list?

Fox, John
In reply to this post by Ivan Calandra-5
Dear John,

This seems to be more complicated than it needs to be. One normally uses coef() to extract coefficients from a model object. Thus

> coef(fitchange)
(Intercept)         pre
-54.1010158   0.6557661
> coef(fitchange)[2]
      pre
0.6557661

Best,
 John

  -------------------------------------------------
  John Fox, Professor Emeritus
  McMaster University
  Hamilton, Ontario, Canada
  Web: http::/socserv.mcmaster.ca/jfox

> On Feb 22, 2019, at 3:26 AM, Sorkin, John <[hidden email]> wrote:
>
> Problem solved:
>
> summary(fitchange)$coefficients[2,1]
>
>
>
> John David Sorkin M.D., Ph.D.
> Professor of Medicine
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
>
> ________________________________
> From: R-help <[hidden email]> on behalf of Ivan Calandra <[hidden email]>
> Sent: Friday, February 22, 2019 2:58:47 AM
> To: [hidden email]
> Subject: Re: [R] Obtaining values of estimates from a regression; How do I get values from a list?
>
> I find that the str() function is really helpful to understand how an object is
> structured, and therefore how to extract part(s) of it.
>
> Try for example:
> str(zz)
> and it might help you understand why zz$coefficients[2,1] is what you were
> looking for.
>
> HTH
> Ivan
>
> --
> Dr. Ivan Calandra
> TraCEr, laboratory for Traceology and Controlled Experiments
> MONREPOS Archaeological Research Centre and
> Museum for Human Behavioural Evolution
> Schloss Monrepos
> 56567 Neuwied, Germany
> +49 (0) 2631 9772-243
> https://www.researchgate.net/profile/Ivan_Calandra
>
> On February 22, 2019 at 8:50 AM Eric Berger <[hidden email]> wrote:
>> You have some choices
>>
>> fitchange$coefficients[2]
>>
>> zz$coefficients[2,1]
>>
>> Note that class(zz$coefficients) shows that it is a matrix.
>>
>> HTH,
>> Eric
>>
>>
>> On Fri, Feb 22, 2019 at 9:45 AM Sorkin, John <[hidden email]>
>> wrote:
>>
>>> I am trying to obtain the coefficients from a regression (performed using
>>> lm). I would like to get the value for the slope (i.e. estimate) for pre
>>> from the following regression:
>>>
>>>
>>> fitchange <- lm(post-pre~pre,data=mydata2)
>>>
>>>
>>> I have tried the following without any success:
>>>
>>>
>>> zz <- summary(fitchange)["coefficients"]
>>> class(zz)
>>> print(zz)
>>> zz[[2,1]]
>>> zz[2,1]
>>> zz["pre","Estimate"]
>>>
>>>
>>> I clearly don't know how to select elements from the list returned by the
>>> summary function.
>>>
>>>
>>> A reproducible version of my code follows:
>>>
>>>
>>> mydata2 <-structure(list(pre = c(71.3302299440613, 86.2703384845455,
>>> 120.941698468568,
>>> 80.9020778388552, 84.9927752038908,
>>> 77.9108032451793, 111.007107108483,
>>> 93.288442414475, 126.097826796255,
>>> 111.63734644637),
>>> post = c(45.9294556667686,
>>> 114.661937978585, 138.501558726477,
>>> 55.355775963925, 97.7906200355594,
>>> 71.1008233796004, 149.308274695789,
>>> 122.828428213951, 143.690814568562,
>>> 116.607579975539)), class = "data.frame",
>>> row.names = c(NA, -10L))
>>>
>>> fitchange <- lm(post-pre~pre,data=mydata2)
>>> zz <- summary(fitchange)["coefficients"]
>>> class(zz)
>>> print(zz)
>>> zz[[2,1]]
>>> zz[2,1]
>>> zz["pre","Estimate"]
>>>
>>>
>>> Any help you can offer would be appreciated.
>>>
>>>
>>>
>>>
>>>
>>>
>>> John David Sorkin M.D., Ph.D.
>>> Professor of Medicine
>>> Chief, Biostatistics and Informatics
>>> University of Maryland School of Medicine Division of Gerontology and
>>> Geriatric Medicine
>>> Baltimore VA Medical Center
>>> 10 North Greene Street
>>> GRECC (BT/18/GR)
>>> Baltimore, MD 21201-1524
>>> (Phone) 410-605-7119
>>> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>>>
>>>
>>> [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> [hidden email] 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]]
>>
>> ______________________________________________
>> [hidden email] 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]]
>
> ______________________________________________
> [hidden email] 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]]
>
> ______________________________________________
> [hidden email] 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.

______________________________________________
[hidden email] 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.
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Re: Obtaining values of estimates from a regression; How do I get values from a list?

R help mailing list-2
Hi,

I was just about to reply with coef() when I saw John's reply come through.

Note that this is covered in An Introduction to R:

  https://cran.r-project.org/doc/manuals/r-release/R-intro.html#Generic-functions-for-extracting-model-information

If your model object is 'MOD', note that you can use:

  coef(MOD)

and

  coef(summary(MOD))

depending upon the specific information that you need.

John provides the output of coef(fitchange) below. To contrast that with:

> coef(summary(fitchange))
               Estimate Std. Error   t value   Pr(>|t|)
(Intercept) -54.1010158 32.7217093 -1.653368 0.13685562
pre           0.6557661  0.3332963  1.967517 0.08466821


These extractor functions are also covered in some of the "See Also" sections of the help pages for the modeling functions such as ?lm.

A key advantage of using the extractor functions, is that they are independent of the underlying object structure. So, while it may be unlikely that the structure of these objects would change in the future, that is not guaranteed. Thus, using the extractor functions is more "future-proof" than directly accessing object components directly.

Regards,

Marc Schwartz


> On Feb 22, 2019, at 8:56 AM, Fox, John <[hidden email]> wrote:
>
> Dear John,
>
> This seems to be more complicated than it needs to be. One normally uses coef() to extract coefficients from a model object. Thus
>
>> coef(fitchange)
> (Intercept)         pre
> -54.1010158   0.6557661
>> coef(fitchange)[2]
>      pre
> 0.6557661
>
> Best,
> John
>
>  -------------------------------------------------
>  John Fox, Professor Emeritus
>  McMaster University
>  Hamilton, Ontario, Canada
>  Web: http::/socserv.mcmaster.ca/jfox
>
>> On Feb 22, 2019, at 3:26 AM, Sorkin, John <[hidden email]> wrote:
>>
>> Problem solved:
>>
>> summary(fitchange)$coefficients[2,1]
>>
>>
>>
>> John David Sorkin M.D., Ph.D.
>> Professor of Medicine
>> Chief, Biostatistics and Informatics
>> University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine
>> Baltimore VA Medical Center
>> 10 North Greene Street
>> GRECC (BT/18/GR)
>> Baltimore, MD 21201-1524
>> (Phone) 410-605-7119
>> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>>
>>
>> ________________________________
>> From: R-help <[hidden email]> on behalf of Ivan Calandra <[hidden email]>
>> Sent: Friday, February 22, 2019 2:58:47 AM
>> To: [hidden email]
>> Subject: Re: [R] Obtaining values of estimates from a regression; How do I get values from a list?
>>
>> I find that the str() function is really helpful to understand how an object is
>> structured, and therefore how to extract part(s) of it.
>>
>> Try for example:
>> str(zz)
>> and it might help you understand why zz$coefficients[2,1] is what you were
>> looking for.
>>
>> HTH
>> Ivan
>>
>> --
>> Dr. Ivan Calandra
>> TraCEr, laboratory for Traceology and Controlled Experiments
>> MONREPOS Archaeological Research Centre and
>> Museum for Human Behavioural Evolution
>> Schloss Monrepos
>> 56567 Neuwied, Germany
>> +49 (0) 2631 9772-243
>> https://www.researchgate.net/profile/Ivan_Calandra
>>
>> On February 22, 2019 at 8:50 AM Eric Berger <[hidden email]> wrote:
>>> You have some choices
>>>
>>> fitchange$coefficients[2]
>>>
>>> zz$coefficients[2,1]
>>>
>>> Note that class(zz$coefficients) shows that it is a matrix.
>>>
>>> HTH,
>>> Eric
>>>
>>>
>>> On Fri, Feb 22, 2019 at 9:45 AM Sorkin, John <[hidden email]>
>>> wrote:
>>>
>>>> I am trying to obtain the coefficients from a regression (performed using
>>>> lm). I would like to get the value for the slope (i.e. estimate) for pre
>>>> from the following regression:
>>>>
>>>>
>>>> fitchange <- lm(post-pre~pre,data=mydata2)
>>>>
>>>>
>>>> I have tried the following without any success:
>>>>
>>>>
>>>> zz <- summary(fitchange)["coefficients"]
>>>> class(zz)
>>>> print(zz)
>>>> zz[[2,1]]
>>>> zz[2,1]
>>>> zz["pre","Estimate"]
>>>>
>>>>
>>>> I clearly don't know how to select elements from the list returned by the
>>>> summary function.
>>>>
>>>>
>>>> A reproducible version of my code follows:
>>>>
>>>>
>>>> mydata2 <-structure(list(pre = c(71.3302299440613, 86.2703384845455,
>>>> 120.941698468568,
>>>> 80.9020778388552, 84.9927752038908,
>>>> 77.9108032451793, 111.007107108483,
>>>> 93.288442414475, 126.097826796255,
>>>> 111.63734644637),
>>>> post = c(45.9294556667686,
>>>> 114.661937978585, 138.501558726477,
>>>> 55.355775963925, 97.7906200355594,
>>>> 71.1008233796004, 149.308274695789,
>>>> 122.828428213951, 143.690814568562,
>>>> 116.607579975539)), class = "data.frame",
>>>> row.names = c(NA, -10L))
>>>>
>>>> fitchange <- lm(post-pre~pre,data=mydata2)
>>>> zz <- summary(fitchange)["coefficients"]
>>>> class(zz)
>>>> print(zz)
>>>> zz[[2,1]]
>>>> zz[2,1]
>>>> zz["pre","Estimate"]
>>>>
>>>>
>>>> Any help you can offer would be appreciated.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> John David Sorkin M.D., Ph.D.
>>>> Professor of Medicine
>>>> Chief, Biostatistics and Informatics
>>>> University of Maryland School of Medicine Division of Gerontology and
>>>> Geriatric Medicine
>>>> Baltimore VA Medical Center
>>>> 10 North Greene Street
>>>> GRECC (BT/18/GR)
>>>> Baltimore, MD 21201-1524
>>>> (Phone) 410-605-7119
>>>> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>>>>

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