How to intantiate a list of data.frames?

Hello,

?I am newbie to R and I want to do this:

for(i in 1:6)
{
? ? ? ?ds[i] <- list(df=data.frame(oilDF[,1],oilDF[,i+2]), df2=data.frame(oilDF2[,1],oilDF2[,i+2]))
}

#oilDF and oilDF2 are 2 data frames with several columns. They have different number of rows

#I want to have for example ds[1]$df, ds[1]$df2 with the respective data.frames.
#How can I instantiate a list of data.frames pairs with different number of rows?

Thank you,
Rui

? ? ? ?[[alternative HTML version deleted]]

Hi Josh,

Sorry, your examples have equal number of rows in both df and df2.
In my situation they haven't.
Strangely, your solution have worked only when I am copy post the code into
the command line.
If I use the code inside of a function I get an error at:
return(ds)
ERROR: arguments imply differing number of rows

Thanks,
Rui

Date: Sat, 21 May 2011 11:46:05 -0700
Subject: Re: [R] How to intantiate a list of data.frames?
From: jwiley.psych at gmail.com
To: ruimaximo at hotmail.com
CC: r-help at r-project.org

Hi Rui,

Here is one option:

ds <- vector("list", 6)
for(i in 1:6) ds[[i]] <- list(df = mtcars[, c(i, i + 2)], df2 =
mtcars[, c(i, i + 2)] + 10)

another could be:

altds <- lapply(1:6, function(x) {
list(df = mtcars[, c(x, x + 2)], df2 = mtcars[, c(x, x + 2)] + 10)
})

all.equal(ds, altds)

For some documentation, see

?vector
?lapply

Cheers,

Josh

On Sat, May 21, 2011 at 10:47 AM, Rui Maximo <ruimaximo at hotmail.com>
wrote:

Hello,

?I am newbie to R and I want to do this:

for(i in 1:6)
{
? ? ? ?ds[i] <- list(df=data.frame(oilDF[,1],oilDF[,i+2]),
df2=data.frame(oilDF2[,1],oilDF2[,i+2]))
}

#oilDF and oilDF2 are 2 data frames with several columns. They have
different number of rows

#I want to have for example ds[1]$df, ds[1]$df2 with the respective
data.frames.
#How can I instantiate a list of data.frames pairs with different number
of rows?

Thank you,
Rui

? ? ? ?[[alternative HTML version deleted]]

--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

I will post the whole function, but I believe the problem is in the 3th
part.
The issue is that oilDF has different number of rows than oilDF2.

Thank you,
Rui

myScan <- function(dirPath, num)
{
#dirPath is the name of the directory where we want to apply the function.
It should be called from the immediate above level without the last 3
characters. For example dirPath="oil_0"
#num is the mussel number

??? #Heart rate
??? startPath=getwd()
??? workPath=paste(startPath,"/", dirPath,"_HR", sep="")
??? setwd(workPath)
??? temp=dir()
??? d=sort(temp)
??? oilDF=read.table (d[1], header=TRUE)
??? oilDF=data.frame(oilDF[,1], oilDF[,2], oilDF[,num+2])
??? for(i in 2:length(d))
??? {
??? ??? temp <- read.table(d[i], header=TRUE)
??? ??? temp=data.frame(temp[,1], temp[,2], temp[,num+2])
??? ??? colnames(temp) <- colnames(oilDF)
??? ??? oilDF=rbind(oilDF,temp)
??? }
??? setwd(startPath)

??? #Valve Gape
??? workPath=paste(startPath,"/", dirPath,"_VG", sep="")
??? setwd(workPath)
??? temp=dir()
??? d=sort(temp)
??? oilDF2=read.table (d[1], header=FALSE)
??? oilDF2=data.frame(oilDF2[,1],oilDF2[,2],oilDF2[,num+3])
??? for(i in 2:length(d))
??? {
??? ??? temp <- read.table(d[i], header=FALSE)
??? ??? temp=data.frame(temp[,1], temp[,2], temp[,num+3])
??? ??? colnames(temp) <- colnames(oilDF2)
??? ??? oilDF2=rbind(oilDF2,temp)
??? }

??? #Pack both signals in a vector of dataframes for each Mussel.
??? ds <- vector("list", 2)
??? timeHR = as.numeric(strptime(paste(oilDF[,1],oilDF[,2]), "%m/%d/%y
%H:%M:%OS"))
??? timeVG = as.numeric(strptime(paste(oilDF2[,1],oilDF2[,2]), "%d/%m/%y
%H:%M:%OS"))
??? ds[[1]] <- data.frame(timeHR,oilDF[,3])
??? ds[[2]] <- data.frame(timeVG,oilDF2[,3])
??? write.csv(ds,paste(startPath, "/", "mussel_", i, dirPath, ".csv",
sep=""))
??? return(ds)
}

Date: Sun, 22 May 2011 11:33:38 -0700
Subject: Re: [R] How to intantiate a list of data.frames?
From: jwiley.psych at gmail.com
To: ruimaximo at hotmail.com
CC: r-help at r-project.org

Hi Rui,

data frames must have the same number of rows, but two different data
frames stored within a list do not need to have the same number of
rows. Can you please post the code that is giving the error?

Josh

On Sun, May 22, 2011 at 9:41 AM, Rui Maximo <ruimaximo at hotmail.com> wrote:

Hi Josh,

Sorry, your examples have equal number of rows in both df and df2.
In my situation they haven't.
Strangely, your solution have worked only when I am copy post the code
into
the command line.
If I use the code inside of a function I get an error at:
return(ds)
ERROR: arguments imply differing number of rows

Thanks,
Rui

Date: Sat, 21 May 2011 11:46:05 -0700
Subject: Re: [R] How to intantiate a list of data.frames?
From: jwiley.psych at gmail.com
To: ruimaximo at hotmail.com
CC: r-help at r-project.org

Hi Rui,

Here is one option:

ds <- vector("list", 6)
for(i in 1:6) ds[[i]] <- list(df = mtcars[, c(i, i + 2)], df2 =
mtcars[, c(i, i + 2)] + 10)

another could be:

altds <- lapply(1:6, function(x) {
list(df = mtcars[, c(x, x + 2)], df2 = mtcars[, c(x, x + 2)] + 10)
})

all.equal(ds, altds)

For some documentation, see

?vector
?lapply

Cheers,

Josh

On Sat, May 21, 2011 at 10:47 AM, Rui Maximo <ruimaximo at hotmail.com>
wrote:

Hello,

?I am newbie to R and I want to do this:

for(i in 1:6)
{
? ? ? ?ds[i] <- list(df=data.frame(oilDF[,1],oilDF[,i+2]),
df2=data.frame(oilDF2[,1],oilDF2[,i+2]))
}

#oilDF and oilDF2 are 2 data frames with several columns. They have
different number of rows

#I want to have for example ds[1]$df, ds[1]$df2 with the respective
data.frames.
#How can I instantiate a list of data.frames pairs with different
number
of rows?

Thank you,
Rui

? ? ? ?[[alternative HTML version deleted]]

--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/

--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/