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As i know there are different ways to drop a column of a data frame in R like
Drop data frame columns by name
How to drop columns by name in a data frame
Remove an entire column from a data.frame in R
Now My question: I have a data frame say df having 400 plus files in the form of nested data frame.
df
[[1]]
SignalIntensity SNR
1 109 6.1823089314 0.8453576915
2 110 10.1727771385 4.3837077591
3 111 7.2922746927 1.0725751161
4 112 8.8984671629 2.3192184908
5 113 9.5910338232 3.7133402249
6 114 7.9850187685 1.5008899345
7 116 7.7893230124 1.3636655582
.
.
.
[[2]]
SignalIntensity SNR
1 109 6.1823089314 0.8453576915
2 110 10.1727771385 4.3837077591
3 111 7.2922746927 1.0725751161
4 112 8.8984671629 2.3192184908
5 113 9.5910338232 3.7133402249
6 114 7.9850187685 1.5008899345
7 116 7.7893230124 1.3636655582
.
.
.
[[3]]
ID SignalIntensity SNR
1 109 6.1823089314 0.8453576915
2 110 10.1727771385 4.3837077591
3 111 7.2922746927 1.0725751161
4 112 8.8984671629 2.3192184908
5 113 9.5910338232 3.7133402249
6 114 7.9850187685 1.5008899345
7 116 7.7893230124 1.3636655582
.
.
.
and so on.....
I want to remove column 1 from all the 400 plus files. The column 1 header may be present or absent.
I know to use df[[1]][,-1] to remove column 1 of first file. In order to do for all the files i have to repeat it 400 or so times to make the work done. There may be 1 or 2 line of code in R to do this. How?? help appreciated.
Final data frame is expected to be like
df
[[1]]
SignalIntensity SNR
1 6.1823089314 0.8453576915
2 10.1727771385 4.3837077591
3 7.2922746927 1.0725751161
4 8.8984671629 2.3192184908
5 9.5910338232 3.7133402249
6 7.9850187685 1.5008899345
7 7.7893230124 1.3636655582
.
.
.
[[2]]
SignalIntensity SNR
1 6.1823089314 0.8453576915
2 10.1727771385 4.3837077591
3 7.2922746927 1.0725751161
4 8.8984671629 2.3192184908
5 9.5910338232 3.7133402249
6 7.9850187685 1.5008899345
7 7.7893230124 1.3636655582
.
.
.
[[3]]
SignalIntensity SNR
1 6.1823089314 0.8453576915
2 10.1727771385 4.3837077591
3 7.2922746927 1.0725751161
4 8.8984671629 2.3192184908
5 9.5910338232 3.7133402249
6 7.9850187685 1.5008899345
7 7.7893230124 1.3636655582
.
.
.
and so on.....
218
Here are multiple ways how to drop one or multiple columns in the R data frame. You can use R base functionality or package like dplyr, but it is not the most time-consuming operation. By knowing how to do that in different ways, you can choose a suitable approach.
How to Drop Columns from Data Frame in R (With Examples) The easiest way to drop columns from a data frame in R is to use the subset () function, which uses the following basic syntax: #remove columns var1 and var3 new_df <- subset (df, select = -c (var1, var3))
The parameter "data" refers to input data frame. "cols" refer to the variables you want to keep / remove. "newdata" refers to the output data frame. To drop variables, use the code below. The drop = 1 implies removing variables which are defined in the second parameter of the function.
The dplyr is an R package for performing common data manipulation tasks. The select () function of dplyr is designed to select columns from a data frame. The ! operator is used to take the complement of a set of variables. It will help us drop columns using the select () function.
One option is with a loop:
for(i in seq_along(df)) {
df[[i]] <- df[[i]][-1]
}
Or without the loop, using lapply:
df2 <- lapply(df, subset, select=-1)
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