@vi@e@gross m@iii@g oii gm@ii@com
2022-Aug-25 16:31 UTC
[R] Getting minimum value of a column according a factor column of a dataframe
Yes, Timothy, the request was not seen by all of us as the same. Indeed if the request was to show a subset of the original data consisting of only the rows that were the minimum for each Code and also showed ties, then the solution is a tad more complex. I would then do something along the lines of what others showed such as generating another column showing the minimum for each row and then showing only rows that matched their value in two columns or whatever was needed. As noted, keeping the output in a specific order was not initially requested. Keeping the data in some order is a common enough request but in this situation, I suspect the order many might want would be the one showing the minimums in order, not the codes in the original order. -----Original Message----- From: Ebert,Timothy Aaron <tebert at ufl.edu> Sent: Thursday, August 25, 2022 11:59 AM To: avi.e.gross at gmail.com Cc: R-help at r-project.org Subject: RE: [R] Getting minimum value of a column according a factor column of a dataframe My assumption (maybe wrong) was that we needed to keep the other variables. I want to find the values of Y, M, D, N, and O for the minimum value of Q within each unique value of Code, keeping the data in the original order. All one need to do is filter Q in the original dataframe by your answer for minQ. Keeping the data in the original order seems unnecessary, but that is what was asked in a later post.
javad bayat
2022-Aug-25 18:02 UTC
[R] Getting minimum value of a column according a factor column of a dataframe
;Dear all
First of all I appreciate you for the answers you have sent. I did the
codes that Rui provided and I got what I wanted.
"
res <- lapply(split(df1, df1$Code), \(x) x[which.min(x$Q),])
res <- do.call(rbind, res)
i <- order(unique(df1$Code))
res[order(i), ]
"
I think I should explain more about my request. I had a large data frame
(11059 rows and 16 columns). The Code column represented the stations code,
totally the number of stations were 128. At each station I had many
measured variables, like Q and N and O, and these variables were measured
in different years and days. The days that data were measured were
different for each station, and due to this reason I had different rows for
stations. For example, station number one (41009) had 158 rows and station
number 2 (41011) had 113 rows. Note that the station's codes are not in
order format (e.g smallest to largest).
Back to my request, I wanted to extract the minimum value of the Q for each
station (based on the Code column). The problem was that I wanted to have
other column values which were measured for this minimum of the Q.
I hope my explanation was clear enough. As I said before, I used the Rui's
codes and I got what I wanted. Although, other solutions provided by others
were all correct.
Regarding my request, unfortunately I faced another problem. I had to
extract the maximum of the Q and put it exactly under the minimum of the Q.
Something like the below one:
"
Code
Y
M
D
Q
N
O
41003
81
1
19
0.16
7.17
2.5
41003
79
8
17
10.21
5.5
7.2
41009
79
2
21
0.218
5.56
4.04
41009 79 10 20 12.24 5.3 7.1
.
.
.
.
"
I extract both min and max according to the codes, and I have 2 dataframes,
one for the minimum values and another for the max values. Both dataframe
have a Code column which is exactly similar.
Can I extract both min and max simultaneously or I have to combine two
dataframes?
I used the rbind and merge function but they did not give the desired
results.> df3 = merge (df1, df2, by = "Code")
The result of this code adds a second dataframe as columns to the first
one. I want the first row of the second dataframe put below the first row
of the first dataframe and so on. I used a function to do this but it seems
it does not work correctly.
> fun2 = function(x,y){
i = 1
for(i in x) {
if (x[i,1] == y[i,1]){
rbind(x[i,],y[i,])
i = i+1
}
}
}> fun2(df1, df2)
Sincerely
On Thu, Aug 25, 2022 at 9:08 PM <avi.e.gross at gmail.com> wrote:
> Yes, Timothy, the request was not seen by all of us as the same.
>
> Indeed if the request was to show a subset of the original data consisting
> of only the rows that were the minimum for each Code and also showed ties,
> then the solution is a tad more complex. I would then do something along
> the
> lines of what others showed such as generating another column showing the
> minimum for each row and then showing only rows that matched their value in
> two columns or whatever was needed.
>
> As noted, keeping the output in a specific order was not initially
> requested.
>
> Keeping the data in some order is a common enough request but in this
> situation, I suspect the order many might want would be the one showing the
> minimums in order, not the codes in the original order.
>
> -----Original Message-----
> From: Ebert,Timothy Aaron <tebert at ufl.edu>
> Sent: Thursday, August 25, 2022 11:59 AM
> To: avi.e.gross at gmail.com
> Cc: R-help at r-project.org
> Subject: RE: [R] Getting minimum value of a column according a factor
> column
> of a dataframe
>
> My assumption (maybe wrong) was that we needed to keep the other variables.
> I want to find the values of Y, M, D, N, and O for the minimum value of Q
> within each unique value of Code, keeping the data in the original order.
> All one need to do is filter Q in the original dataframe by your answer for
> minQ.
>
> Keeping the data in the original order seems unnecessary, but that is what
> was asked in a later post.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>
--
Best Regards
Javad Bayat
M.Sc. Environment Engineering
Alternative Mail: bayat194 at yahoo.com
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