CODEWITHSUNDEEP
rmacoscsv
cdwhiteiv
cdwhiteiv

Reputation: 107

Count rows in multiple csv's, write to csv's as new column in descending order

I need help editing multiple csv's within a folder. I need to count the number of rows in each file, and add a new column to the files. The new column should have the number of rows as the first row in the column, and then descend by 1 for each subsequent row.

Current:
ID  V1  V2  V3
1   0.4625  0.917
2   0.9324  0.248
3   0.6691  0.781
4   0.1935  0.330

Proposed:
ID  V1   V2  V3   newcol  
1   0.4  25  0.9  5
2   0.9  24  0.2  4
3   0.6  91  0.7  3
4   0.1   5  0.3  2
5   0.2  44  0.5  1

Anyone have any ideas? I've been playing around with the terminal and trying to do it that way. I also have some minor experience with r. I'm also using a mac if that helps.

Thanks!

Upvotes: 1

Views: 164

Answers (2)

cdwhiteiv
cdwhiteiv

Reputation: 107

Got it! With akrun's guidance I was able to successfully add a column to each csv, with the rows in the new column in descending order. I was then able to write it back to the original files!

filenames <- list.files(path=".../pathoffolder", pattern=".*csv")

for(i in filenames) {
   filepath <- file.path(".../pathoffolder", paste(i))
   assign(i,filepath)
   df <- read.csv(filepath)
   df$newcol <- rev(seq_len(nrow(df)))
   write.csv(df, filepath, quote = FALSE, row.names = FALSE)
}

Upvotes: 1

akrun
akrun

Reputation: 887951

We can do

df1$newcol <- rev(seq_len(nrow(df1)))

Or

df1$newcol <-  nrow(df1):1

Upvotes: 2

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