Re: [R] howto get the number of columns and column names of multiply data frames
Thanks for your replies. Both, Don and Stevens solutions worked well. Best regards Frank __ R-help@r-project.org 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.
Re: [R] howto get the number of columns and column names of multiply data frames
## You can use get()
for ( i in 1:n) {
nm <- paste('dataframe',i,sep='')
cat( ncol( get(nm)), 'columns in',nm,'\n') )
}
## or
nms <- ls(pattern='dataframe')
for (nm in nms) cat( ncol(get(nm)) , 'columns in',nm,'\n') )
}
(Assuming I have balanced parantheses, that is --
my email software doesn't check that like Emacs
does!)
Storing the dataframes as elements of a list, as
Steve Lianoglou suggested, lets you avoid using
the get() function.
You could also use the count.fields() function to
check whether the files have the correct number
of columns even before you read the data it. Or
make a pass through the files reading in only the
first line as data, and comparing those as data
rather than as a names attribute of a dataframe.
-Don
At 5:29 PM +0200 8/9/09, Frank Schäffer wrote:
Hi,
I' ve read in several files with measurements into R data frames(works
flawlessly). Each dataframe is named by the location of measurement and
contains hundreds of rows and about 50 columns like this
dataframe1.
date measurment_1 mesurement_n
1
2
3
..
..
..
n
For further processing I need to check whether or not ncol and colnames are
the same for all dataframes.
Also I need to add a new column to each dataframe with contain the name of the
dataframe, so that this column can be treated as factor in later processing
(after merging some seleted dataframes to one)
I tried out
for (i in 1:length(ls()){
print(ncol(ls()[i])
}
but this does not work because r returns a "character" for i and therefore
"NULL" as result.
Reading the output of ls() into a list also does not work.
How can I accomplish this task??
Best regards and thanks
Frank
__
R-help@r-project.org 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.
--
--
Don MacQueen
Environmental Protection Department
Lawrence Livermore National Laboratory
Livermore, CA, USA
925-423-1062
__
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] howto get the number of columns and column names of multiply data frames
Hi,
On Aug 9, 2009, at 11:29 AM, Frank Schäffer wrote:
Hi,
I' ve read in several files with measurements into R data frames(works
flawlessly). Each dataframe is named by the location of measurement
and
contains hundreds of rows and about 50 columns like this
dataframe1.
date measurment_1 mesurement_n
1
2
3
..
..
..
n
Just as an aside, it's somehow considered more R-idiomatic to store
all of these tables in a list (of tables) and access them as
mydata[[1]], mydata[[2]], ..., mydata[[n]]. Assuming the datafiles are
'filename.1.txt', 'filename.2.txt', etc. You might do this like so:
mydata <- lapply(paste('filename', 1:n, 'txt', sep='.'), read.table,
header=TRUE, sep=...)
To test that all colnames are the same, you could do something like.
names1 <- colnames(mydata[[1]])
all(sapply(2:n, function(dat) length(intersect(names1,
colnames(mydata[[n]]))) == length(names1)))
For further processing I need to check whether or not ncol and
colnames are
the same for all dataframes.
Also I need to add a new column to each dataframe with contain the
name of the
dataframe, so that this column can be treated as factor in later
processing
(after merging some seleted dataframes to one)
I tried out
for (i in 1:length(ls()){
print(ncol(ls()[i])
}
but this does not work because r returns a "character" for i and
therefore
"NULL" as result.
Reading the output of ls() into a list also does not work.
How can I accomplish this task??
If you still want to do it this way, see: ?get
for example:
for (varName in paste('dataframe', 1:n, sep='')) {
cat(colnames(get(varName)))
}
HTH,
-steve
--
Steve Lianoglou
Graduate Student: Computational Systems Biology
| Memorial Sloan-Kettering Cancer Center
| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact
__
R-help@r-project.org 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.
[R] howto get the number of columns and column names of multiply data frames
Hi,
I' ve read in several files with measurements into R data frames(works
flawlessly). Each dataframe is named by the location of measurement and
contains hundreds of rows and about 50 columns like this
dataframe1.
date measurment_1 mesurement_n
1
2
3
..
..
..
n
For further processing I need to check whether or not ncol and colnames are
the same for all dataframes.
Also I need to add a new column to each dataframe with contain the name of the
dataframe, so that this column can be treated as factor in later processing
(after merging some seleted dataframes to one)
I tried out
for (i in 1:length(ls()){
print(ncol(ls()[i])
}
but this does not work because r returns a "character" for i and therefore
"NULL" as result.
Reading the output of ls() into a list also does not work.
How can I accomplish this task??
Best regards and thanks
Frank
__
R-help@r-project.org 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.
