# Beginners tutorial with R – Strings

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## Beginners tutorial with R – Strings

Any value written within a pair of single quote or double quotes in R is treated as a string. Internally R stores every string within double quotes, even when you create them with single quote.

## Rules Applied in String Construction

• The quotes at the beginning and end of a string should be both double quotes or both single quote. They can not be mixed.
• Double quotes can be inserted into a string starting and ending with single quote.
• Single quote can be inserted into a string starting and ending with double quotes.
• Double quotes can not be inserted into a string starting and ending with double quotes.
• Single quote can not be inserted into a string starting and ending with single quote.

### Examples of Valid Strings

Following examples clarify the rules about creating a string in R.

```a <- 'Start and end with single quote'
print(a)

b <- "Start and end with double quotes"
print(b)

c <- "single quote ' in between double quotes"
print(c)

d <- 'Double quotes " in between single quote'
print(d)```

When the above code is run we get the following output −

```[1] "Start and end with single quote"
[1] "Start and end with double quotes"
[1] "single quote ' in between double quote"
[1] "Double quote " in between single quote"
```

### Examples of Invalid Strings

```e <- 'Mixed quotes"
print(e)

f <- 'Single quote ' inside single quote'
print(f)

g <- "Double quotes " inside double quotes"
print(g)```

When we run the script it fails giving below results.

```Error: unexpected symbol in:
"print(e)
f <- 'Single"
Execution halted
```

## String Manipulation

### Concatenating Strings – paste() function

Many strings in R are combined using the paste() function. It can take any number of arguments to be combined together.

### Syntax

The basic syntax for paste function is −

```paste(..., sep = " ", collapse = NULL)
```

Following is the description of the parameters used −

•  represents any number of arguments to be combined.
• sep represents any separator between the arguments. It is optional.
• collapse is used to eliminate the space in between two strings. But not the space within two words of one string.

### Example

```a <- "Hello"
b <- 'How'
c <- "are you? "

print(paste(a,b,c))

print(paste(a,b,c, sep = "-"))

print(paste(a,b,c, sep = "", collapse = ""))```

When we execute the above code, it produces the following result −

```[1] "Hello How are you? "
[1] "Hello-How-are you? "
[1] "HelloHoware you? "
```

### Formatting numbers & strings – format() function

Numbers and strings can be formatted to a specific style using format() function.

### Syntax

The basic syntax for format function is −

```format(x, digits, nsmall, scientific, width, justify = c("left", "right", "centre", "none"))
```

Following is the description of the parameters used −

• x is the vector input.
• digits is the total number of digits displayed.
• nsmall is the minimum number of digits to the right of the decimal point.
• scientific is set to TRUE to display scientific notation.
• width indicates the minimum width to be displayed by padding blanks in the beginning.
• justify is the display of the string to left, right or center.

### Example

```# Total number of digits displayed. Last digit rounded off.
result <- format(23.123456789, digits = 9)
print(result)

# Display numbers in scientific notation.
result <- format(c(6, 13.14521), scientific = TRUE)
print(result)

# The minimum number of digits to the right of the decimal point.
result <- format(23.47, nsmall = 5)
print(result)

# Format treats everything as a string.
result <- format(6)
print(result)

# Numbers are padded with blank in the beginning for width.
result <- format(13.7, width = 6)
print(result)

# Left justify strings.
result <- format("Hello", width = 8, justify = "l")
print(result)

# Justfy string with center.
result <- format("Hello", width = 8, justify = "c")
print(result)```

When we execute the above code, it produces the following result −

```[1] "23.1234568"
[1] "6.000000e+00" "1.314521e+01"
[1] "23.47000"
[1] "6"
[1] "  13.7"
[1] "Hello   "
[1] " Hello  "
```

### Counting number of characters in a string – nchar() function

This function counts the number of characters including spaces in a string.

### Syntax

The basic syntax for nchar() function is −

```nchar(x)
```

Following is the description of the parameters used −

• x is the vector input.

### Example

```result <- nchar("Count the number of characters")
print(result)```

When we execute the above code, it produces the following result −

```[1] 30
```

### Changing the case – toupper() & tolower() functions

These functions change the case of characters of a string.

### Syntax

The basic syntax for toupper() & tolower() function is −

```toupper(x)
tolower(x)
```

Following is the description of the parameters used −

• x is the vector input.

### Example

```# Changing to Upper case.
result <- toupper("Changing To Upper")
print(result)

# Changing to lower case.
result <- tolower("Changing To Lower")
print(result)```

When we execute the above code, it produces the following result −

```[1] "CHANGING TO UPPER"
[1] "changing to lower"
```

### Extracting parts of a string – substring() function

This function extracts parts of a String.

### Syntax

The basic syntax for substring() function is −

```substring(x,first,last)
```

Following is the description of the parameters used −

• x is the character vector input.
• first is the position of the first character to be extracted.
• last is the position of the last character to be extracted.

### Example

```# Extract characters from 5th to 7th position.
result <- substring("Extract", 5, 7)
print(result)```

When we execute the above code, it produces the following result −

`[1] "act"`

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