I know there are several questions regarding the "apply one function to multiple data frames"-issue. However, I coundn't find a solution to my problem but I think I got close to it using a solution from this question:
Same function over multiple data frames in R
I have 12 data frames with 4 columns each. The second one contains the data as an integer (e.g. 20161014, so %Y%m%d).
To get it into 2016-10-14 I used
TX_SOUID100758.txt[,2]<-as.Date(as.character(TX_SOUID100758.txt[,2]), "%Y%m%d")
Since I want to apply this function on all 15 data frames I tried
zch_filelist <- list.files(path=path, pattern="*.txt")
for (file in zch_filelist){
assign(file, read.csv(paste(path, file, sep=''),na.strings = -9999))
}
lapply(zch_filelist, function(x) (as.Date(as.character(x[2]), "%Y%m%d")))
I used the previously created list of file names when I imported the files into R.
However, it is not working. I guess the mistake is the indexing in the as.date function.
Any help is greatly appreciated.
Thanks!
Related
I'm new to R am trying reorganise my data based on the sampleID
I've used the split() function in R which has does exactly what I wanted it to and stored my information in new data.frames
My question is now that they are in separate data.frames how do I access them individually for further processing?
My code goes as follows
splitList.list = list()
for (i in 1:31)
{
splitList.list[[i]] = split(chromList.list[[i]], chromList.list[[i]]$sampleID)
}
splitList.list[[1]]
I take the files I have (31 files), split them and store them in a list. This much works. I get an output that looks like this
This can be repeated with any of list elements and work. I now what to do some processing on separately on each data.frame but don't know how to access just one of these. Please help
I am new to R and coding in general, so please bear with me.
I have a spreadsheet that has 7 sheets, 6 of these sheets are formatted in the same way and I am skipping the one that is not formatted the same way.
The code I have is thus:
lst <- lapply(2:7,
function(i) read_excel("CONFIDENTIAL Ratio 062018.xlsx", sheet = i)
)
This code was taken from this post: How to import multiple xlsx sheets in R
So far so good, the formula works and I have a large list with 6 sub lists that appears to represent all of my data.
It is at this point that I get stuck, being so new I do not understand lists yet, and really need the lists to be merged into one single data frame that looks and feels like the source data (so columns and rows).
I cannot work out how to get from a list to a single data frame, I've tried using R Bind and other suggestions from here, but all seem to either fail or only partially work and I end up with a data frame that looks like a list etc.
If each sheets has the same number of columns (ncol) and same names (colnames) then this will work. It needs the dplyr pacakge.
require(dplyr)
my_dataframe <- bind_rows(my_list)
I know that there are many threads called this but either the advice within hasn't worked or I haven't understood it.
I have read what was an SPSS file into R.
I cleaned some variables and added new ones.
By this point the file size is 1,000 MB.
I wanted to write it into a CSV to look at it more easily but it just stops responding - file too big I guess.
So instead I want to create a subset of only the variables I need. I tried a couple of things
(besb <- bes[, c(1, 7, 8)])
data1 <- bes[,1:8]
I also tried referring to variables by name:
nf <- c(bes$approveGov, bes$politmoney)
All these attempts return errors with number of dimensions.
Therefore could somebody please explain to me how to create a reduced subset of variables preferably using variable names?
An easy way to subset variables from a data.frame is with the dplyr package. You can select variables with their bare names. For example:
library(dplyr)
nf <- select(bes, approveGov, politmoney)
It's fast for large data frames too.
I have multiple csv-files in one folder. I want to load each csv-file in this folder into one separate data frame. Next, I want to extract certain elements from this data frame into a matrix and calculate the mean of all these matrixes.
setwd("D:\\data")
group_1<-list.files()
a<-length(group_1)
mferg_mean<-data.frame
for(i in 1:a)
{
assign(paste0("mferg_",i),read.csv(group_1[i],header=FALSE,sep=";",quote="",dec=",",col.names=1:90))
}
As there are 11 csv-files in the folder I now have the data frames
mferg_1
to
mferg_11
How can I address each data frame in this loop? As mentioned, I want to extract certain elements from each data frame to a matrix. I would imagine it something like this:
assign(paste0("mferg_matrix_",i),mferg_i[1:5,1:10])
But this obviously does not work because R does not recognize mferg_i in the loop. How can I address this data frame?
This is not something you should probably be using assign for in the first place. Working with a bunch of different data.frames in R is a mess, but working with a list of data.frames is much easier. Try reading your data with
group_1<-list.files()
mferg <- lapply(group_1, function(filename) {
read.csv(filename,header=FALSE,sep=";",quote="",dec=",",col.names=1:90))
})
and you get each each value with mferg[[1]], mferg[[1]], etc. And then you can create a list of extractions with
mferg_matrix <- lapply(mferg, function(x) x[1:5, 1:10])
This is the more R-like way to do things.
But technically you can use get to retrieve values like you use assign to create them. For example
assign(paste0("mferg_matrix_",i),get(paste0("mferg_",i))[1:5,1:10])
but again, this is probably not a smart strategy in the long run.
Edit: I've corrected the typo in the coding (copy and paste error). I can't add an example of the csv files, as its too complex to model in a simple example (I tried..)
I've spent hours looking through similarly titled questions to solve a for loop problem in R, and have tried a lot of different approaches, but I'm having no luck.
I have many different csv files, each of which has a set of 10 separate strings (variables) identifying a specific row (e.g., names = c("Delta values", "Scream factor", "nightmare mode"). Two rows below such a string, I need the max value of that row of data. I can create loops scanning files for such a value in single csv files using the following
test files-
test1.csv, test2.csv, test3.csv test4.csv
names<-list.files(pattern=".csv")
DF <- NULL
for (i in names){
dat <- read.csv(i, header=FALSE, stringsAsFactors=FALSE)
index <- which(dat=="Delta values", arr.ind=TRUE)
row=as.numeric(rownames(dat)[index[1]])
aver=dat[row+2,]
p=max(na.omit(as.numeric(aver)))
DF=rbind(DF, p)
colnames(DF)=dat[index]}
However, my problem comes in trying to generalize it, so that I get a data frame returned indicating the file each value was retrieved from as a row (not "p") and looping over the files so that I can retrieve the next several variables, while appending to the same data frame so that I end up with a data frame listing by row the filename the variable was derived from, and each variable listed in a separate column.
I'm pretty sure I need a nested loop listing the values I want to retrieve as calculated by "p" but I can't find any good examples describing how to iteratively loop using such an approach, and append the new variables to the growing data frame while staying consistent with the row numbering by file.
please help!