Running different Regressions using for loops
On Sep 28, 2012, at 4:35 AM, Krunal Nanavati wrote:
Ok...I am sorry for the misunderstanding.... what I am trying to do is....
Perhaps (and that is a really large 'perhaps'):
lm.list2 <- list()
lm.means <- list()
for(i in seq_along(pricemedia)){
regr <- paste(pricemedia[i], trendseason, sep = "+")
fmla <- paste(response, regr, sep = "~")
lm.list2[[i]] <- lm(as.formula(fmla), data = tryout2) }
lm.means[[i]] <- mean(lm.list2[[i]]$coefficients[c("Price1", "Media1")]
}
When I run...this set of statements....the 1st regression to be run, will have Price 1, Media 1...as X variables....and in the second loop it will have Price 1 & Media 2 .... So, what I was thinking is...if I can generate inside the for loop....the mean for Price 1 and Media 1 during the 1st loop....and then mean for Price 1 and Media 2 during the second loop...and so on...for all the 10 regressions Is the method that I was trying appropriate...or is there a better method there...I am sorry for the earlier explanation, I hope this one makes it more understandable
One generally want ones methods to be determinate while allowing the results to be approximate. Had you followed the posting guide a offered a reproducible example it would have been much more "understandable".
Thanks for your time...and all the quick replies -----Original Message----- From: Rui Barradas [mailto:ruipbarradas at sapo.pt] Sent: 28 September 2012 16:49 To: Krunal Nanavati Cc: David Winsemius; r-help at r-project.org Subject: Re: [R] Running different Regressions using for loops Ok, if I'm understanding it well, you want the mean value of Price1, , Price5? I don't know if it makes any sense, the coefficients already are mean values, but see if this is it. price.coef <- sapply(lm.list, function(x) coef(x)[2]) mean(price.coef) Rui Barradas Em 28-09-2012 12:07, Krunal Nanavati escreveu:
Hi,
Yes the thing that you provided...works fine....but probably I should
have asked for some other thing.
Here is what I am trying to do....
I am trying to get the mean of Price variable....so I am entering the
below function:
mean(names(lm.list2[[2]]$coefficient[2] ))
but this gives me an error....
[1] NA
Warning message:
In mean.default(names(lm.list2[[2]]$coefficient[2])) :
argument is not numeric or logical: returning NA
I thought by getting the text from the list variable...will help me
generate the mean for that text...which is a variable in the
data...say Price 1, Media 2....and so on
Is this a proper approach...if it is...then something more needs to be
done with the function that you provided.
If not, is there a better way...to generate the mean of a particular
variable inside the " for loop " used earlier...given below:
lm.list2 <- list()
for(i in seq_along(pricemedia)){
regr <- paste(pricemedia[i], trendseason, sep = "+")
fmla <- paste(response, regr, sep = "~")
lm.list2[[i]] <- lm(as.formula(fmla), data = tryout2) }
Thanks & Regards, Krunal Nanavati 9769-919198 -----Original Message----- From: Rui Barradas [mailto:ruipbarradas at sapo.pt] Sent: 28 September 2012 16:02 To: Krunal Nanavati Cc: David Winsemius; r-help at r-project.org Subject: Re: [R] Running different Regressions using for loops Hello, Try names(lm.list2[[2]]$coefficient[2] ) Rui Barradas Em 28-09-2012 11:29, Krunal Nanavati escreveu:
Ok...this solves a part of my problem
When I type " lm.list2[2] " ...I get the following output
[[1]]
Call:
lm(formula = as.formula(fmla), data = tryout2)
Coefficients:
(Intercept) Price2 Media1 Distri1 Trend
Seasonality
13491232 -5759030 -1520 34370 48628
445351
When I enter " lm.list2[[2]]$coefficient[2] " it gives me the below
output
Price2
-5759030
And when I enter " lm.list2[[2]]$coefficient[[2]] " ...I get the
number...which is -5759030
I am looking out for a way to get just the " Price2 "....is there a
statement for that??
Thanks & Regards,
Krunal Nanavati
9769-919198
-----Original Message-----
From: Rui Barradas [mailto:ruipbarradas at sapo.pt]
Sent: 28 September 2012 15:18
To: Krunal Nanavati
Cc: David Winsemius; r-help at r-project.org
Subject: Re: [R] Running different Regressions using for loops
Hello,
To access list elements you need `[[`, like this:
summ.list[[2]]$coefficients
Or Use the extractor function,
coef(summ.list[[2]])
Rui Barradas
Em 28-09-2012 07:23, Krunal Nanavati escreveu:
Hi Rui, Excellent!! This is what I was looking for. Thanks for the help. So, now I have stored the result of the 10 regressions in
"summ.list
<- lapply(lm.list2, summary)" And now once I enter " sum.list "....it gives me the output for
all
the 10 regressions... I wanted to access a beta coefficient of one of the regressions....say "Price2+Media1+Trend+Seasonality"...the result of
which is stored in"
sum.list[2] " I entered the below statement for accessing the Beta coefficient for Price2...
summ.list[2]$coefficients[2]
NULL But this is giving me " NULL " as the output... What I am looking for, is to access a beta value of a particular variable from a particular regression output and use it for further
analysis.
Can you please help me out with this. Greatly appreciate, you guys efforts. Thanks & Regards, Krunal Nanavati 9769-919198 -----Original Message----- From: Rui Barradas [mailto:ruipbarradas at sapo.pt] Sent: 27 September 2012 21:55 To: Krunal Nanavati Cc: David Winsemius; r-help at r-project.org Subject: Re: [R] Running different Regressions using for loops Hello, Inline. Em 27-09-2012 13:52, Krunal Nanavati escreveu:
Hi, Thanks for all your help. I am stuck again, but with a new problem, on similar lines. I have taken the problem to the next step now...i have now added 2
"for"
loops... 1 for the Price variable...and another for the Media variable I have taken 5 price variables...and 2 media variables with the "trend and seasonality"(appearing in all of them)....so in all there will be 10 regression to run now Price 1, Media 1 Price 1, Media 2 Price 2, Media 1' Price 2, Media 2 ...and so on I have built up a code for it...
tryout=read.table("C:\\Users\\Krunal\\Desktop\\R
tryout.csv",header=T,sep=",")
cnames <- names(tryout)
price <- cnames[grep("Price", cnames)] media <-
cnames[grep("Media", cnames)] resp <- cnames[1] regr <-
cnames[7:8] lm.list <- vector("list", 10) for(i in 1:5)
+ {
+ regress <- paste(price[i], paste(regr, collapse = "+"), sep =
+ "+") for(j in 1:2) {
+ regress1 <- paste(media[j],regress,sep="+") fmla <- paste(resp,
+ regress1, sep = "~") lm.list[[i]] <- lm(as.formula(fmla), data =
+ tryout) } }
summ.list <- lapply(lm.list, summary) summ.list
But it is only running...5 regressions...only Media 1 along with the 5 Price variables & Trend & Seasonality is regressed on Volume...giving only 5 outputs I feel there is something wrong with the " lm.list[[i]] <- lm(as.formula(fmla), data = tryout)" statement.
No, I don't think so. If it's giving you only 5 outputs the error is
probably in the fmla construction. Put print statements to see the
results of those paste() instructions.
Supposing your data.frame is now called tryout2,
price <- paste("Price", 1:5, sep = "") media <- paste("Media", 1:2,
sep = "") pricemedia <- apply(expand.grid(price, media,
stringsAsFactors = FALSE), 1, paste, collapse="+")
response <- "Volume"
trendseason <- "Trend+Seasonality" # do this only once
lm.list2 <- list()
for(i in seq_along(pricemedia)){
regr <- paste(pricemedia[i], trendseason, sep = "+")
fmla <- paste(response, regr, sep = "~")
lm.list2[[i]] <- lm(as.formula(fmla), data = tryout2) }
The trick is to use ?expand.grid
Hope this helps,
Rui Barradas
I am not sure about its placement...whether it should be in loop 2 or in loop 1 Can you please help me out?? Thanks & Regards, Krunal Nanavati 9769-919198 -----Original Message----- From: Rui Barradas [mailto:ruipbarradas at sapo.pt] Sent: 27 September 2012 16:22 To: David Winsemius Cc: Krunal Nanavati; r-help at r-project.org Subject: Re: [R] Running different Regressions using for loops Hello, Just to add that you can also lapply(lm.list, coef) with a different output. Rui Barradas Em 27-09-2012 09:24, David Winsemius escreveu:
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.
[[alternative HTML version deleted]]
David Winsemius, MD Alameda, CA, USA
David Winsemius, MD Alameda, CA, USA