How to convert all words of a string or categorical variable in an R data frame to uppercase?

Most of the times the format of the data we get is not we are looking for therefore, we need to change that according to our need. When the levels of categorical variables are represented by words instead of numbers then we can convert those levels to lowercase or to uppercase. Sometimes, this is done just to make the information look user friendly. Mostly, we find that the values are in lowercase, so we can convert it to the upper case with the help of sapply function.

Example

Consider the below data frame −

> x1<-letters[1:20]
> x2<-20:1
> x3<-rep(c("india","china","usa","saudi arabia","jordan"),times=4)
> df<-data.frame(x1,x2,x3)
> df
  x1 x2 x3
 1 a 20 india
 2 b 19 china
 3 c 18 usa
 4 d 17 saudi arabia
 5 e 16 jordan
 6 f 15 india
 7 g 14 china
 8 h 13 usa
 9 i 12 saudi arabia
10 j 11 jordan
11 k 10 india
12 l  9 china
13 m  8 usa
14 n  7 saudi arabia
15 o  6 jordan
16 p  5 india
17 q  4 china
18 r  3 usa
19 s  2 saudi arabia
20 t  1 jordan
> df_new<-as.data.frame(sapply(df, toupper))
> df_new
x1 x2 x3
1 A 20 INDIA
2 B 19 CHINA
3 C 18 USA
4 D 17 SAUDI ARABIA
5 E 16 JORDAN
6 F 15 INDIA
7 G 14 CHINA
8 H 13 USA
9 I 12 SAUDI ARABIA
10 J 11 JORDAN
11 K 10 INDIA
12 L 9 CHINA
13 M 8 USA
14 N 7 SAUDI ARABIA
15 O 6 JORDAN
16 P 5 INDIA
17 Q 4 CHINA
18 R 3 USA
19 S 2 SAUDI ARABIA
20 T 1 JORDAN

Let’s have a look at one more example, where we have first letter of second variable in upper case −

> y1<-letters[26:7]
> y2<-rep(c("Statistics","Biology","Psychology","Marketing","Physics"),each=4)
> y3<-rep(c(2,4,6,8),times=5)
> df_y<-data.frame(y1,y2,y3)
> df_y
y1 y2 y3
1 z Statistics 2
2 y Statistics 4
3 x Statistics 6
4 w Statistics 8
5 v Biology 2
6 u Biology 4
7 t Biology 6
8 s Biology 8
9 r Psychology 2
10 q Psychology 4
11 p Psychology 6
12 o Psychology 8
13 n Marketing 2
14 m Marketing 4
15 l Marketing 6
16 k Marketing 8
17 j Physics 2
18 i Physics 4
19 h Physics 6
20 g Physics 8

> df_y_new<-as.data.frame(sapply(df_y, toupper))
> df_y_new
y1 y2 y3
1 Z STATISTICS 2
2 Y STATISTICS 4
3 X STATISTICS 6
4 W STATISTICS 8
5 V BIOLOGY 2
6 U BIOLOGY 4
7 T BIOLOGY 6
8 S BIOLOGY 8
9 R PSYCHOLOGY 2
10 Q PSYCHOLOGY 4
11 P PSYCHOLOGY 6
12 O PSYCHOLOGY 8
13 N MARKETING 2
14 M MARKETING 4
15 L MARKETING 6
16 K MARKETING 8
17 J PHYSICS 2
18 I PHYSICS 4
19 H PHYSICS 6
20 G PHYSICS 8