David,
As others have said, there are many possible answers for a vague enough
question.
For one-time data it is often easiest to simply change the data source as you
say you did in EXCEL.
Deleting the 18th row can easily be done in R and might make sense if you get
daily data and decided the 18th reporting station is not reliable and should
always be excluded. As has been shown, the usual paradigm in R is to filter the
data through a set of conditions and a very simple one is to specify which
indices in rows and/or columns to exclude.
If you already have your data in mydata.old, then you can make a mydata.new
that excludes that 18th row with something as simple as:
mydata.new <- mydata.old[ -18, ]
Since your question was not focused, the answer mentioned that it is common to
delete based on all kinds of conditions. An example would be if you did not
want to remove row 18 specifically but any row where a column says the
collector/reporter of the info was "Smith" which may remove many rows in the
data, or you wanted only data with a column giving a date in 2021 and not
before or after.
This filter method is not a deletion per se, but a selective retention, and
often has the same result. If your goal includes making the deletion of
selected data permanent, of course, it is wise then to save the altered data in
another file so later use starts with what you want.
Actually removing a row from an original data.frame is not something people
normally do. A data.frame is a list of vectors of some length and generally
does not allow operations that might produce vectors of unequal length. You can
set the entire row to be filled with NA if you want but removing the actual row
in-place is the kind of thing I do not normally see. In a sense, R is wasteful
that way as you often end up making near-copies of your data and sometimes
simply re-assigning the result to the same variable and expecting the old
version to be garbage collected. As I said, the paradigm is selection more than
alteration/deletion.
It is, of course, possible to create your own data structures where you could
do something closer to a deletion of a row while leaving the rest in place but
there likely is no need for your small amount of data.
Note columns in R can be deleted easily because they are a top level entry in a
LIST. mydata$colname <- NULL or similar variants will remove a column cleanly
in the original data.frame. But as noted, rows in R do not really exist other
than as a construct that tries to bind the nth elements of each underlying
vector representing the columns.
Of course we now can have list-columns in things like tibbles which makes me
wonder ...
-----Original Message-----
From: R-help <r-help-boun...@r-project.org> On Behalf Of Parkhurst, David
Sent: Sunday, September 18, 2022 8:49 AM
To: CALUM POLWART <polc1...@gmail.com>
Cc: R-help@r-project.org
Subject: Re: [R] Remove line from data file
Thank you for your reply. I meant from the dataframe, but that s one of the
terms I had forgotten. I created that from read.csv, the csv file coming from
Excel. Last night I went ahead and made the change(s) using Excel.
For future reference, when I look at your solutions below, what do you mean by
value to delete ? Could that just be a row number? I was wanting to delete
something like the 18th row in the dataframe?
From: CALUM POLWART <polc1...@gmail.com>
Date: Sunday, September 18, 2022 at 7:25 AM
To: Parkhurst, David <parkh...@indiana.edu>
Cc: R-help@r-project.org <R-help@r-project.org>
Subject: Re: [R] Remove line from data file From the file? Or the data frame
once its loaded?
What format is the file? CSV?
Do you know the line that needs deleted?
mydf <- read.csv("myfile.csv")
mydf2 <- mydf[-columnName == "valuetodelete", ] # Note the - infront of column
name # or perhaps columnName != "value to delete", ]
write.csv(mydf2, "mydeletedfile.csv")
On Sun, 18 Sep 2022, 10:33 Parkhurst, David,
<parkh...@indiana.edu<mailto:parkh...@indiana.edu>> wrote:
I ve been retired since 06 and have forgotten most of R. Now I have a use for
it. I ve created a data file and need to delete one row from it. How do I do
that?
DFP (iPad)
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