How to repeat this statement in R probably using apply() - r

Question

It might seem a silly question but how to repeat this line for 152 times and I would not like to use a for loop,since later it will not be efficient with larger data sets:
reviews = as.vector(t(mydata)[,1])
mydata is a row in a data.frame and
reviews is an array of characters, also
[,1] is just the first row
The output could be a matrix or worst case a data.frame.
I tried something like this, but it did not work :
testing = apply(mydata, 1, function(x) {as.vector(t(mydata[,x]))})
Error in t(mydata)[, x] : subscript out of bounds
Thanks.
EDIT:
Quick data sample:
> reviews = as.vector(t(mydata)[,1])
> class(reviews)
[1] "character"
> length(reviews)
[1] 14
> reviews
[1] "I was involuntarily"
[2] "I was in transit"
[3] "My initial flight"
[4] "That still left"
[5] "After disembarking"
[6] "customs and proceed to my gate."
[7] "I arrived"
[8] "When my boarding pass was scanned"
[9] "No reason was given for the bump."
[10] "The UA gate staff"
[11] "I boarded Air Canada."
[12] "After arriving"
[13] "I spent 5 hours"
[14] NA
mydata data.frame:
> class(mydata)
[1] "data.frame"
> length(mydata[,1])
[1] 152
> mydata[,1]
[1] I was involuntarily... .
[2] First time... .
...
...
152 Levels: First time . ...
I have about 30.000 of these, but I want to start small, so only 152 of paragraphs split in individual sentence and put into a data.frame. Each row in the data.frame has 5-15 sentences.
I want to to be able to access each row as an array since I need to perform some action on each row of the data.frame
Packages used: plyr, sentiment(downloaded from here and installed manually)
EDIT 2:
dput(myData[1:6, 1:6])
structure(list(V1 = structure(c(70L, 41L, 94L, 114L, 47L, 49L),
.Label = c(" Air Canada",
"their service",
"hours for de-icing",
"have flown BA",
"my booking",
"If the video screen",
"Frankfurt flights",
"and another 150 lines of text data",

Answer 1

Here's a recommended way to ask a question, focusing on the fact that your actual data is too big, too complicated, or too private to share.
Question: how to apply a function on each row of a data.frame?
My data:
# make up some data
s <- "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
mydata <- as.data.frame(matrix(strsplit(s, '\\s')[[1]][1:18], nrow=3, ncol=6), stringsAsFactors=FALSE)
mydata
## V1 V2 V3 V4 V5 V6
## 1 Lorem sit adipiscing do incididunt et
## 2 ipsum amet, elit, eiusmod ut dolore
## 3 dolor consectetur sed tempor labore magna
If you have data that you can use directly, then as has been suggested multiple times in the comments, the use of dput is helpful:
mydata <- structure(list(V1 = c("Lorem", "ipsum", "dolor"),V2 = c("sit", "amet,", "consectetur"), V3 = c("adipiscing", "elit,", "sed"),
V4 = c("do", "eiusmod", "tempor"), V5 = c("incididunt", "ut", "labore"), V6 = c("et", "dolore", "magna")), .Names = c("V1",
"V2", "V3", "V4", "V5", "V6"), row.names = c(NA, -3L), class = "data.frame")
In either order, state (i) what you are trying to do, and (ii) what you have tried and how it is not working.
My desired output:
Converting a row into a vector is ... confusing. A row is already a vector, so I don't know what you are ultimately trying to do. So, I'll come up with something short an to the point: I want the words on each row to be in reverse alphabetical order, perhaps like this:
## V1 V2 V3 V4 V5 V6
## 1 sit Lorem incididunt et do adipiscing
## 2 ut ipsum elit, eiusmod dolore amet,
## 3 tempor sed magna labore dolor consectetur
This is a good time to show the code you've tried, errors you've encountered, and/or how the unerring output is not what you intended.
Answer, generically:
Several ways to do something to each row:
Use apply, though this breaks if you have numeric and character intermingled. If you try this, you'll see that the output is actually the transpose of what you may think, in which case you'll need to wrap (and all of the other *apply-based suggestions here) with t(...). It's a little confusing, but it's necessary here. Oh, and they'll all be a matrix class which can easily be converted to data.frame if needed.
ret <- apply(mydata, 1, function(r) {
do_something(r)
})
Use sapply or lapply on row indices. Note that these are returning lists or vectors of results, so you'll need to convert into whatever format you ultimately need.
ret <- sapply(1:nrow(mydata), function(i) {
do_something(mydata[i,])
})
# if you need to keep each row's results rather encapsulated, use one of the following:
ret <- sapply(1:nrow(mydata), function(i) {
do_something(mydata[i,])
}, simplify=FALSE)
ret <- lapply(1:nrow(mydata), function(i) {
do_something(mydata[i,])
})
Use foreach and iterators.
library(foreach)
library(iterators)
ret <- foreach(df=iter(mydata, by='row'), .combine=rbind) %do% {
do_something(df) # just one row of mydata this time
}
In the case of my (contrived) question, here are several ways to do it:
as.data.frame(t(apply(mydata, 1, function(r) sort(r, decreasing=TRUE))))
## V1 V2 V3 V4 V5 V6
## 1 sit Lorem incididunt et do adipiscing
## 2 ut ipsum elit, eiusmod dolore amet,
## 3 tempor sed magna labore dolor consectetur
as.data.frame(t(sapply(1:nrow(mydata), function(i) sort(mydata[i,], decreasing=TRUE))))
## same output
library(foreach)
library(iterators)
## notice the use of as.character(...), perhaps still a blasphemy
## to the structure of a data.frame
ret <- foreach(df=iter(mydata, by='row'), .combine=rbind) %do% {
sort(as.character(df), decreasing=TRUE)
}
ret
## [,1] [,2] [,3] [,4] [,5] [,6]
## result.1 "sit" "Lorem" "incididunt" "et" "do" "adipiscing"
## result.2 "ut" "ipsum" "elit," "eiusmod" "dolore" "amet,"
## result.3 "tempor" "sed" "magna" "labore" "dolor" "consectetur"