fmtr

The fmtr package helps format data. The package aims to simulate the basic functionality of SAS® formats, but with R.

Formatting may be assigned to data frame columns using the format, width, and justify attributes. Formatting is then applied by calling the fdata function. fdata returns a new data frame with the specified formatting applied. This method of formatting provides much greater control over data formatting than the base R format function.

Here is a example:

# Construct data frame from state vectors
df <- data.frame(state = state.abb, area = state.area)[1:10, ]

# Calculate percentages
df$pct <- df$area / sum(state.area) * 100

# Before formatting 
df

#    state   area         pct
# 1     AL  51609  1.42629378
# 2     AK 589757 16.29883824
# 3     AZ 113909  3.14804973
# 4     AR  53104  1.46761040
# 5     CA 158693  4.38572418
# 6     CO 104247  2.88102556
# 7     CT   5009  0.13843139
# 8     DE   2057  0.05684835
# 9     FL  58560  1.61839532
# 10    GA  58876  1.62712846

# Create state name lookup list
name_lookup <- state.name
names(name_lookup) <- state.abb

# Assign formats
formats(df) <- list(state = name_lookup,                         
                    area  = function(x) format(x, big.mark = ","), 
                    pct   = "%.1f%%") 

# Apply formats
fdata(df)

#          state    area   pct
# 1      Alabama  51,609  1.4%
# 2       Alaska 589,757 16.3%
# 3      Arizona 113,909  3.1%
# 4     Arkansas  53,104  1.5%
# 5   California 158,693  4.4%
# 6     Colorado 104,247  2.9%
# 7  Connecticut   5,009  0.1%
# 8     Delaware   2,057  0.1%
# 9      Florida  58,560  1.6%
# 10     Georgia  58,876  1.6%

Key Features

fmtr contains the following key features:

• The fdata function to apply formatting to any data frame or tibble.
• The fapply function to apply formatting to any vector.
• The formats and fattr functions to easily assign formatting attributes.
• The value and condition functions to create a new user-defined format.
• The flist function to create a formatting list.

How to use fdata()

Data can be formatted by assigning formats to the format attribute of the columns in your dataframe or tibble, and then by calling the fdata() function on that data. A sample program is as follows:

# Set up data frame
df <- mtcars[1:10, c("mpg", "cyl")]

# Define and assign formats
attr(df$mpg, "format") <- value(condition(x >= 20, "High"),
                                condition(x < 20, "Low"))

attr(df$cyl, "format") <- function(x) format(x, nsmall = 1)

# Apply formatting
fdata(df)

Here is the mtcars subset before formatting:

#                    mpg cyl
# Mazda RX4         21.0   6
# Mazda RX4 Wag     21.0   6
# Datsun 710        22.8   4
# Hornet 4 Drive    21.4   6
# Hornet Sportabout 18.7   8
# Valiant           18.1   6
# Duster 360        14.3   8
# Merc 240D         24.4   4
# Merc 230          22.8   4
# Merc 280          19.2   6

And here is the mtcars subset after formatting:

#                    mpg cyl
# Mazda RX4         High 6.0
# Mazda RX4 Wag     High 6.0
# Datsun 710        High 4.0
# Hornet 4 Drive    High 6.0
# Hornet Sportabout Low  8.0
# Valiant           Low  6.0
# Duster 360        Low  8.0
# Merc 240D         High 4.0
# Merc 230          High 4.0
# Merc 280          Low  6.0

You may apply formatting to variables of any data type: character, numeric, date, etc. Internally, the fdata() function is using the fapply() function on each column in the data frame. If there is no format assigned to a column, that column is returned unaltered.

How to use fapply()

The fapply() function applies a format to a vector, factor, or list. This function may be used independently of the fdata() function. Here is an example:

v1 <- c("A", "B", "C", "B")
v1

# [1] "A" "B" "C" "B"

fmt1 <- value(condition(x == "A", "Label A"),
              condition(x == "B", "Label B"),
              condition(TRUE, "Other"))

fapply(v1, fmt1)

# "Label A" "Label B"   "Other" "Label B" 

One advantage of using fapply() is that your original data is not altered. The formatted values are assigned to a new object. If your original data changes, the formatting function should be reapplied to maintain consistency with the original data.

What kind of formats are available

Data can be formatted with several different types of objects:

• A formatting string
• A named vector
• A user-defined format
• A vectorized function
• A formatting list

You can use the type of formatting object that is most suitable to your data and situation. Each type of formatting object has it's own strengths and weaknesses.

Formatting String

The formatting functions accept formatting strings such as those associated with the Base R format and sprintf functions. If the data type of the vector is a date or datetime, fapply will use the format codes associated with the format function. For other data types, fapply will use the format codes associated with sprintf. Here is an example:

v1 <- c(1.367, 8.356, 4.583, 2.873)

fapply(v1, "%.1f%%")

[1] "1.4%" "8.4%" "4.6%" "2.9%"

Named vectors

Data may be formatted using a named vector as a lookup. Simply ensure that the names on the formatting vector correspond to the values in the data vector.
The advantage of using a named vector for formatting is its simplicity. The disadvantage is that it only works with character values. Here is an example of formatting using a named vector:

v1 <- c("A", "B", "C", "B")

fmt1 <- c(A = "Label A", B = "Label B", C= "Label C")

fapply(v1, fmt1)

# "Label A" "Label B" "Label C" "Label B" 

User-defined formats

The fmtr package provides custom functions for creating user-defined formats, in a manner that is similar to a SAS® user-defined format. These functions are value and condition. The value function accepts one or more conditions. The conditions function accepts an expression/label pair. A user-defined format has the advantage of a clear and flexible syntax. It is excellent for categorizing data. Here is an example of a user-defined format:

v1 <- c("A", "B", NA, "C")

fmt2 <- value(condition(is.na(x), "Missing"),
              condition(x == "A", "Label A"),
              condition(x == "B", "Label B"),
              condition(TRUE, "Other"))
              
fapply(v1, fmt2)

# "Label A" "Label B"   "Missing" "Other" 

Vectorized functions

Vectorized functions provide the most powerful way of formatting data. Vectorized functions can be user-defined, or wrapping an available packaged function. The vectorized function has the advantage of being nearly limitless in the types of formatting you can perform. The drawback is that a vectorized function can be more complicated to write. Here is an example of formatting with a user-defined, vectorized function:

v1 <- c("A", "B", NA, "C")

fmt2 <- Vectorize(function(x) {
    
    if (is.na(x)) 
      ret <- "Missing"
    else if (x %in% c("A", "B"))
      ret <- paste("Label", x)
    else 
      ret <- "Other"
    
    return(ret)
    
  })
  
fapply(v1, fmt2)

# "Label A" "Label B"   "Missing" "Other" 

A formatting list

Sometimes data needs to be formatted differently for each row. This situation is difficult to deal with in any language.
But it can be made easy in R with the fmtr package and a formatting list.

A formatting list is a list that contains one or more of the three types of formatting objects described above. A formatting list can be applied in two different ways: in order, or with a lookup.

By default, the list is applied in order. That means the first format in the list is applied to the first item in the vector, the second format in the list is applied to the second item in the vector, and so on. The list is recycled if the number of list items is shorter than the number of values in the vector.

For the lookup method, the formatting object is specified by a lookup vector. The lookup vector should contain names associated with the elements in the formatting list. The lookup vector should also contain the same number of items as the data vector. For each item in the data vector, fmtr will look up the appropriate format from the formatting list, and apply that format to the corresponding data value.

The following is an example of a lookup style formatting list:

# Set up data
v1 <- c("num", "char", "date", "char", "date", "num")
v2 <- list(1.258, "H", as.Date("2020-06-19"),
           "L", as.Date("2020-04-24"), 2.8865)

df <- data.frame(type = v1, values = I(v2))
df

#    type     values
# 1   num      1.258
# 2  char          H
# 3  date 2020-06-19
# 4  char          L
# 5  date 2020-04-24
# 6   num     2.8865

# Set up formatting list
lst <- flist(type = "row", lookup = v1,
             num = function(x) format(x, digits = 2, nsmall = 1),
             char = value(condition(x == "H", "High"),
                          condition(x == "L", "Low"),
                          condition(TRUE, "NA")),
             date = function(x) format(x, format = "%y-%m"))

# Assign formatting list to values column
attr(df$values, "format") <- lst


# Apply formatting
fdata(df)

#   type values
# 1  num    1.3
# 2 char   High
# 3 date  20-06
# 4 char    Low
# 5 date  20-04
# 6  num    2.9

Convenience Functions

The formats() function

The formats associated with a data frame can be easily extracted or assigned with the formats() function. This function returns or accepts a named list of formatting objects. The names of the list items
correspond to the names of the columns in the data frame. This function is useful when you want to assign formats to many columns.

The fattr() function

The fattr() function helps assign formatting attributes to a vector or data frame column. The fattr() function can assign the format, width, and justify attributes all at once. These attributes are passed in as arguments to the fattr() function, instead of as properties on a call to attr().

Other convenience functions

The logr package contains several other functions for setting attributes easily. These include the widths and justification functions to set columns widths and column justification on an entire data frame. The package also includes class testing functions like is.format and is.flist.