Running different Regressions using for loops

On Sep 26, 2012, at 10:31 PM, Krunal Nanavati wrote:

Dear Rui,

Thanks for your time.

I have a question though, when I run the 5 regression, whose outputs are
stored in ?lm.list[i]?, I only get the coefficients for the Intercept,
Price, Trend & Seasonality as below

lm.list[1]

[[1]]

Call:

lm(formula = as.formula(fmla), data = tryout)

Coefficients:

(Intercept)       Price4        Trend  Seasonality

    9923123     -2606826        64616       551392

summ.list <- lapply(lm.list, summary)
coef.list <- lapply(summ.list, coef)
coef.list

I am also looking out for t stats and p value and R squared.

For the r.squared

rsq.vec <- sapply(summ.list, "$", "r.squared")
adj.rsq <- sapply(summ.list, "$", "adj.r.squared")

Do you know,
how can I get all these statistics. Also, why is ? as.formula ? used in the
lm function. It should work without that as well, right?

No.

Can you please tell me, why the code that I had written, does not work with
R. I thought it should work perfectly.

In R there is a difference between expression objects and character objects.

Thanks & Regards,



Krunal Nanavati

9769-919198



*From:* Rui Barradas [mailto:ruipbarradas at sapo.pt]
*Sent:* 26 September 2012 17:13
*To:* Krunal Nanavati
*Cc:* r-help at r-project.org
*Subject:* Re: [R] Running different Regressions using for loops



Hello,

Try the following.


#cnames <- names(tryout)  # in your code, use this one
cnames <- c("Volume", "Price1", "Price2", "Price3", "Price4", "Price5",
"Trend", "Seasonaliy")

price <- cnames[grep("Price", cnames)]
resp <- cnames[1]
regr <- cnames[7:8]

#lm.list <- vector("list", 5)
for(i in 1:5){
    regress <- paste(price[i], paste(regr, collapse = "+"), sep = "+")
    fmla <- paste(resp, regress, sep = "~")
    print(fmla)
    #lm.list[[i]] <- lm(as.formula(fmla), data = tryout)
}

Hope this helps,

Rui Barradas

Em 26-09-2012 08:08, Krunal Nanavati escreveu:

Hi,


I am trying to run many different regressions using a FOR Loop.


The input data that is read into R has the following variables

?         Volume
?         Price2
?         Price3
?         Price4
?         Price5
?         Trend
?         Seasonality

I want to run 5 regressions, with the Volume as an dependent variable and

Price, Trend & Seasonality as independent variables. I have read the above

mentioned variables in a variable called ?tryout?



I am entering the following syntax in R


for(i in 1:5)

+ {
+ result[i]=lm(Volume~Price[i]+Trend+Seasonaliy,data=tryout)
+ summary(result[i])
+ }

After running these lines?I am getting the following error message
Error in eval(expr, envir, enclos) : object 'Price' not found

Can someone help me out with this error message. Appreciate for your time

and consideration.



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David Winsemius, MD
Alameda, CA, USA