Add a Prefix to All Rows in R

Add a prefix to all rows in R

Just use paste0 to combine strings.

For example,

chrs$endsnp = paste0('end', chrs$endsnp)

or using paste and specifing the separator between the strings

chrs$endsnp = paste('end', chrs$endsnp, sep='')

Add a prefix and suffix to each row of a dataframe but no suffix to the last row and then collapse all

I think that the best approach is to add prefix and suffix to all,
then extract the string to remove the last OR

library(tidyverse)
library(glue)

x <- data.frame(products = c("foo","bar","foobar"))

x$products <- glue("BRAND_NAME LIKE '% {x$products} %' OR ")

now collapse to single string

glue_collapse(x$products) %>%

now the string extraction

str_extract(., ".+(?= OR $)")

This last statement looks ahead for the space-OR-space at the end ($) for a match, and includes all characters up to but not including this match

Add prefix and suffix to list values R

I would vectorize this as follows

indx <- which(data[, -1] != "", arr.ind = TRUE) # Find all non-empty incidences 
data[, -1][indx] <- paste("Here this is", data[, -1][indx], "completed.")

Adding a prefix only to specific rows in dataframe R

Try:

Fold_change$Well <- as.character(Fold_change$Well) # change column class from factor to character first
Fold_change$Well[1:288] <- paste0('Plate_1_', Fold_change$Well[1:288])

Add prefix to every row of a column if it doesn't contain it

Another option...

dt$value <- gsub("^([^_].*)", "_\\1", dt$value)

dt
  id value
1  1    _a
2  2    _b
3  3    _c

The first regex looks for the start of a string followed by something that is not _, plus any following characters, and replaces it with the second regex, which is _ plus the capture group from the first regex.

Adding prefix to specific R columns

You aren't obliged to use grepl(). It's possible to use gsub() instead. Since gsub() if no match found, returns unchanged values, you can change your column names on the fly, without intermediate indexing step:

Example data set

sed.seed(66248086) 

(
  dat <- data.frame(
    ID         = 1:3,
    EXPFRQ     = runif(3),
    EXPMETADAT = sample(c(T, F), 3, T),
    .EXPGRP    = sample(LETTERS[1:3], 3, T),
    EXPOUT     = sample(c('*', '**', '***'), 3, T),
    NOTES      = c("Bad project...", "What is in this tube?", "Blot, blot western baby")
    )
  )

#   ID       EXPFRQ EXPMETADAT .EXPGRP EXPOUT                   NOTES
# 1  1 0.5483680151      FALSE       C      *          Bad project...
# 2  2 0.0628816469      FALSE       B     **   What is in this tube?
# 3  3 0.0001267055       TRUE       B    *** Blot, blot western baby

Actually where renaming takes place

Just give to gsub() your pattern, and call the chunk it found using back-reference (\\1):

colnames(dat) <- gsub('^(EXP[A-Z]{3})$', 'New_\\1', colnames(dat))

Result

dat

#   ID   New_EXPFRQ EXPMETADAT .EXPGRP New_EXPOUT                   NOTES
# 1  1 0.5483680151      FALSE       C          *          Bad project...
# 2  2 0.0628816469      FALSE       B         **   What is in this tube?
# 3  3 0.0001267055       TRUE       B        *** Blot, blot western baby

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Note: Please, reade the note written by @akrun under his answer!

How to merge rows with the same prefix in a data frame?

df %>%
  group_by(col1 = str_remove(col1, "\\d+"))%>%
  summarise(counts = sum(counts))

Adding a prefix to each column name in each dataframe in a list of dataframes R

In tidyverse, we can use imap with rename_with :

library(dplyr)
library(purrr)

imap(l1, ~.x %>% 
  rename_with(function(x) c(paste(.y, x[1], sep = '_'), paste0('lab_', x[-1]))))

#$Fe
#  Fe_Determination_No lab_2 lab_3 lab_4 lab_5 lab_7  lab_8 lab_10 lab_12
#1                   1 55.94 56.83 56.39 56.32 56.48 56.382   56.3  56.11
#2                   2 55.70 56.54 56.43 56.29 56.40 56.258   56.5  56.46
#3                   3 56.59 56.18 56.53 56.31 56.54 56.442   56.2  56.10
#4                   4 56.50 56.50 56.31 56.32 56.43 56.258   56.5  56.35
#5                   5 55.98 56.51 56.47 56.39 56.73 56.532   56.7  56.36
#6                   6 55.93 56.34 56.35 56.32 56.62 56.264   56.5  56.37

3$SiO2
#  SiO2_Determination_No lab_2 lab_3 lab_4 lab_5 lab_7 lab_8   lab_10 lab_12
#1                     1  7.63  7.84  7.67  7.91  7.77 7.936 7.872685   7.64
#2                     2  7.65  7.69  7.74  7.84  7.83 7.685 7.851292   7.71
#3                     3  7.73  7.59  7.62  7.96  7.76 7.863 7.872685   7.71
#4                     4  7.67  7.77  7.81  7.87  7.78 7.838 7.722933   7.65
#5                     5  7.67  7.74  7.66  7.84  7.65 7.828 7.680147   7.82
#6                     6  7.67  7.64  7.80  7.92  7.74 7.767 7.615967   7.68

#$Al2O3
#  Al2O3_Determination_No lab_2 lab_3 lab_4 lab_5 lab_7 lab_8   lab_10 lab_12
#1                      1  2.01  2.01  2.00  2.02  1.88 2.053 2.002830   2.09
#2                      2  2.02  2.01  2.03  2.02  1.90 2.044 2.021725   2.05
#3                      3  2.03  2.00  1.99  2.05  1.89 2.041 2.021725   1.96
#4                      4  2.01  2.02  2.01  2.03  1.88 2.038 1.983936   2.09
#5                      5  2.02  2.02  2.01  2.02  1.88 2.008 2.002830   2.06
#6                      6  2.00  2.03  2.01  2.03  1.87 2.020 2.021725   2.02 

Or in base R with Map :

Map(function(x, y) {
  names(x) <- c(paste(y, names(x)[1], sep = '_'), paste0('lab_', names(x[-1])))
  x
}, l1, names(l1))

Add a prefix to column names

You have misread the help file. Here's the argument to look at:

do.NULL: logical. If FALSE and names are NULL, names are created.

Notice the and in that description. Your names are no longer NULL, so using prefix won't work.

Instead, use something like this:

> m2 <- cbind(1,1:4)
> colnames(m2) <- c("x","Y")
> colnames(m2) <- paste("Sub", colnames(m2), sep = "_")
> m2
     Sub_x Sub_Y
[1,]     1     1
[2,]     1     2
[3,]     1     3
[4,]     1     4

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