error message from read.csv in loop
Hello Kai, Just as you did to store the data inside of rr. Try class(rr[[1]]) or class(rr[[2]]) and so on to explore a bit more. The variable rr is a list that contains dataframes within it. To access the dataframes you must use the syntax rr[[i]] where i is the index of the element of the list (or the number of the dataframe in your case). For example: df1 <- rr[[1]] class(df1) # Check if this is class "data.frame". df2 <- rr[[2]] class(df2) You can also try other ways to store the dataframes more efficiently. This is just a quick-and-dirty solution to the code you provided. I recommend reading more about lists in R to understand how they work and how they differ from other data structures like vectors. Hope this helps, Warm regards. Migdonio G.
On Fri, Jul 9, 2021 at 2:24 PM Kai Yang <yangkai9999 at yahoo.com> wrote:
Hi Migdonio,
I did try your code:
# Initialize the rr variable as a list.
rr <- as.list(rep(NA, nrow(ora)))
# Run the for-loop to store all the CSVs in rr.
for (j in 1:nrow(ora))
{
mycol <- ora[j,"fname"]
mycsv <- paste0(mycol,".csv")
rdcsv <- noquote(paste0("w:/project/_Joe.B/Oracle/data/", mycsv))
rr[[j]] <- read.csv(rdcsv)
}
this code is working, but rr is not a data frame, R said: Large list ( 20
elements .....). how can I use it as a data frame one by one?
Thank you for your help
Kai
On Friday, July 9, 2021, 11:39:59 AM PDT, Migdonio Gonz?lez <
migdonio.gonzalez02 at gmail.com> wrote:
It seems that your problem is that you are using single quotes inside of
the double quotes. This is not necessary. Here is the corrected for-loop:
for (j in 1:nrow(ora))
{
mycol <- ora[j,"fname"]
mycsv <- paste0(mycol,".csv")
rdcsv <- noquote(paste0("w:/project/_Joe.B/Oracle/data/", mycsv))
rr <- read.csv(rdcsv)
}
Also note that the rr variable will only store the last CSV, not all CSV.
You will need to initialize the rr variable as a list to store all CSVs if
that is what you require. Something like this:
# Initialize the rr variable as a list.
rr <- as.list(rep(NA, nrow(ora)))
# Run the for-loop to store all the CSVs in rr.
for (j in 1:nrow(ora))
{
mycol <- ora[j,"fname"]
mycsv <- paste0(mycol,".csv")
rdcsv <- noquote(paste0("w:/project/_Joe.B/Oracle/data/", mycsv))
rr[[j]] <- read.csv(rdcsv)
}
Regards
Migdonio G.
On Fri, Jul 9, 2021 at 1:10 PM Kai Yang via R-help <r-help at r-project.org>
wrote:
Hello List,
I use for loop to read csv difference file into data frame rr. The data
frame rr will be deleted after a comparison and go to the next csv file.
Below is my code:
for (j in 1:nrow(ora))
{
mycol <- ora[j,"fname"]
mycsv <- paste0(mycol,".csv'")
rdcsv <- noquote(paste0("'w:/project/_Joe.B/Oracle/data/", mycsv))
rr <- read.csv(rdcsv)
}
but when I run this code, I got error message below:
Error in file(file, "rt") : cannot open the connection
In addition: Warning message:
In file(file, "rt") :
cannot open file
''w:/project/_Joe.B/Oracle/data/ASSAY_DEFINITIONS.csv'': No such file or
directory
so, I checked the rdcsv and print it out, see below:
[1] 'w:/project/_Joe.B/Oracle/data/ASSAY_DEFINITIONS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/ASSAY_DISCRETE_VALUES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/ASSAY_QUESTIONS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/ASSAY_RUNS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/DATA_ENTRY_PAGES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/DISCRETE_VALUES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/ENTRY_GROUPS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/GEMD_CODELIST_GROUPS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/GEMD_CODELIST_VALUES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/GEMD_LOT_DEFINITIONS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/GEMD_SAMPLES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/MOLECULAR_WAREHOUSE.csv'
[1] 'w:/project/_Joe.B/Oracle/data/QUESTION_DEFINITIONS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/QUESTION_GROUPS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/RESPONDENTS.csv'
[1] 'w:/project/_Joe.B/Oracle/data/RESPONSES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/SAMPLE_LIST.csv'
[1] 'w:/project/_Joe.B/Oracle/data/SAMPLE_LIST_NAMES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/SAMPLE_PLATE_ADDRESSES.csv'
[1] 'w:/project/_Joe.B/Oracle/data/STORAGE_UNITS.csv'
it seems correct. I copy and paste it into a code :
rr <- read.csv( 'w:/project/_Joe.B/Oracle/data/RESPONDENTS.csv')
and it works fine.
Can someone help me debug where is the problem in my for loop code?
Thanks,
Kai
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