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Adding character in matrix in R

I import csv by.

data<-read.csv('test.csv')


and then data has value

> data
name a b c d
1 a 1 2 1 1
2 b 2 2 2 4


now i wish to add row at the bottom of data so,I add

results <- c('aa',2,3,4,5)
data[nrow(data)+1,]<-results


But it cause me warring and character value is not inserted.

Warning message:
In `[<-.factor`(`*tmp*`, iseq, value = "aa") :
invalid factor level, NA generated


and data has value =

> data
name a b c d
1 a 1 2 1 1
2 b 2 2 2 4
3 <NA> 2 3 4 5


but i want to have

> data
name a b c d
1 a 1 2 1 1
2 b 2 2 2 4
3 aa 2 3 4 5


I am new in R and have tried for the ans for many hours so any help will be appreciated.Thank you.

dt = data.frame(x=c("A","B"), y=1:2, stringsAsFactors = T); dt[3,] = c("C",3); dt = data.frame(x=c("A","B"), y=1:2, stringsAsFactors = F); dt[3,] = c("C",3)

4 Answers
4

This should work.

data <- read.csv('test.csv', stringsAsFactors = FALSE)


In a short explanation, read.csv treat every character column as a factor by default. Factor are a special class of data that can only take a few values determined at its creation.

Could you please try following:(I am putting data in here you could use read.csv)

read.csv

dat <- read.table(text = "name a b c d
1 a 1 2 1 1
2 b 2 2 2 4",
header = TRUE,stringsAsFactors = FALSE)
dat
results <- c('aa',2,3,4,5)
rbind(dat,results)


Output(without using stringAsFactors = FALSE):

stringAsFactors = FALSE

name a b c d
1 a 1 2 1 1
2 b 2 2 2 4
3 <NA> 2 3 4 5
Warning message:
In `[<-.factor`(`*tmp*`, ri, value = "aa") :
invalid factor level, NA generated


Output without warning message:

name a b c d
1 a 1 2 1 1
2 b 2 2 2 4
3 aa 2 3 4 5


There are several problems here:

c(...)

data

To fix these problems use as.is = TRUE in read.csv and use list instead of c:

as.is = TRUE

read.csv

list

c

data <- read.csv("test.csv", as.is = TRUE)
data[nrow(data) + 1, ] <- list('aa',2,3,4,5)


giving:

> data
name a b c d
1 a 1 2 1 1
2 b 2 2 2 4
3 aa 2 3 4 5


The file in reproducible form is generated from:

Lines <- "name a b c d
1 a 1 2 1 1
2 b 2 2 2 4
"
temp <- read.table(text = Lines, as.is = TRUE)
write.csv(temp, "test.csv", row.names = FALSE, quote = FALSE)


Include 'aa' as one of the levels and it should work with the OP's factor column. Also, as list can hold different type instead of a vector (formed with c), assign the next row with a list as input

levels

factor

list

type

c

list

levels(data$name) <- c(levels(data$name), 'aa')
data[nrow(data) +1,] <- list('aa', 2, 3, 4, 5)
data
# name a b c d
#1 a 1 2 1 1
#2 b 2 2 2 4
#3 aa 2 3 4 5


data <- structure(list(name = structure(1:2, .Label = c("a", "b"),
class = "factor"),
a = 1:2, b = c(2L, 2L), c = 1:2, d = c(1L, 4L)), .Names = c("name",
"a", "b", "c", "d"), row.names = c("1", "2"), class = "data.frame")


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