R: Update a Data Frame or Cleanup a Data Frame after Importing

upData {Hmisc} | R Documentation

## Update a Data Frame or Cleanup a Data Frame after Importing

### Description

`cleanup.import` will correct errors and shrink the size of data frames. By default, double precision numeric variables are changed to integer when they contain no fractional components. Infinite values or values greater than 1e20 in absolute value are set to NA. This solves problems of importing Excel spreadsheets that contain occasional character values for numeric columns, as S converts these to `Inf` without warning. There is also an option to convert variable names to lower case and to add labels to variables. The latter can be made easier by importing a CNTLOUT dataset created by SAS PROC FORMAT and using the `sasdict` option as shown in the example below. `cleanup.import` can also transform character or factor variables to dates.

`upData` is a function facilitating the updating of a data frame without attaching it in search position one. New variables can be added, old variables can be modified, variables can be removed or renamed, and `"labels"` and `"units"` attributes can be provided. Observations can be subsetted. Various checks are made for errors and inconsistencies, with warnings issued to help the user. Levels of factor variables can be replaced, especially using the `list` notation of the standard `merge.levels` function. Unless `force.single` is set to `FALSE`, `upData` also converts double precision vectors to integer if no fractional values are present in a vector. `upData` is also used to process R workspace objects created by StatTransfer, which puts variable and value labels as attributes on the data frame rather than on each variable. If such attributes are present, they are used to define all the labels and value labels (through conversion to factor variables) before any label changes take place, and `force.single` is set to a default of `FALSE`, as StatTransfer already does conversion to integer.

Variables having labels but not classed `"labelled"` (e.g., data imported using the `haven` package) have that class added to them by `upData`.

The `dataframeReduce` function removes variables from a data frame that are problematic for certain analyses. Variables can be removed because the fraction of missing values exceeds a threshold, because they are character or categorical variables having too many levels, or because they are binary and have too small a prevalence in one of the two values. Categorical variables can also have their levels combined when a level is of low prevalence.

### Usage

    cleanup.import(obj, labels, lowernames=FALSE,
                   force.single=TRUE, force.numeric=TRUE, rmnames=TRUE,
                   big=1e20, sasdict, print, datevars=NULL, datetimevars=NULL,
                   dateformat='%F',
                   fixdates=c('none','year'), charfactor=FALSE)

    upData(object, ...,
           subset, rename, drop, keep, labels, units, levels, force.single=TRUE,
           lowernames=FALSE, caplabels=FALSE, moveUnits=FALSE,
           charfactor=FALSE, print=TRUE, html=FALSE)

    dataframeReduce(data, fracmiss=1, maxlevels=NULL,  minprev=0, print=TRUE)

### Arguments

`obj` | a data frame or list
`object` | a data frame or list
`data` | a data frame
`force.single` | By default, double precision variables are converted to single precision (in S-Plus only) unless `force.single=FALSE`. `force.single=TRUE` will also convert vectors having only integer values to have a storage mode of integer, in R or S-Plus.
`force.numeric` | Sometimes importing will cause a numeric variable to be changed to a factor vector. By default, `cleanup.import` will check each factor variable to see if the levels contain only numeric values and `""`. In that case, the variable will be converted to numeric, with `""` converted to NA. Set `force.numeric=FALSE` to prevent this behavior.
`rmnames` | set to ‘F’ to not have ‘cleanup.import’ remove ‘names’ or ‘.Names’ attributes from variables
`labels` | a character vector the same length as the number of variables in `obj`. These character values are taken to be variable labels in the same order of variables in `obj`. For `upData`, `labels` is a named list or named vector with variables in no specific order.
`lowernames` | set this to `TRUE` to change variable names to lower case. `upData` does this before applying any other changes, so variable names given inside arguments to `upData` need to be lower case if `lowernames==TRUE`.
`big` | a value such that values larger than this in absolute value are set to missing by `cleanup.import`
`sasdict` | the name of a data frame containing a raw imported SAS PROC CONTENTS CNTLOUT= dataset. This is used to define variable names and to add attributes to the new data frame specifying the original SAS dataset name and label.
`print` | set to `TRUE` or `FALSE` to force or prevent printing of the current variable number being processed. By default, such messages are printed if the product of the number of variables and number of observations in `obj` exceeds 500,000. For `dataframeReduce` set `print` to `FALSE` to suppress printing information about dropped or modified variables. Similar for `upData`.
`datevars` | character vector of names (after `lowernames` is applied) of variables to consider as a factor or character vector containing dates in a format matching `dateformat`. The default is `"%F"` which uses the yyyy-mm-dd format.
`datetimevars` | character vector of names (after `lowernames` is applied) of variables to consider to be date-time variables, with date formats as described under `datevars` followed by a space followed by time in hh:mm:ss format. `chron` is used to store date-time variables. If all times in the variable are 00:00:00 the variable will be converted to an ordinary date variable.
`dateformat` | for `cleanup.import` is the input format (see `strptime`)
`fixdates` | for any of the variables listed in `datevars` that have a `dateformat` that `cleanup.import` understands, specifying `fixdates` allows corrections of certain formatting inconsistencies before the fields are attempted to be converted to dates (the default is to assume that the `dateformat` is followed for all observation for `datevars`). Currently `fixdates='year'` is implemented, which will cause 2-digit or 4-digit years to be shifted to the alternate number of digits when `dateform` is the default `"%F"` or is `"%y-%m-%d"`, `"%m/%d/%y"`, or `"%m/%d/%Y"`. Two-digits years are padded with `20` on the left. Set `dateformat` to the desired format, not the exceptional format.
`charfactor` | set to `TRUE` to change character variables to factors if they have fewer than n/2 unique values. Null strings and blanks are converted to `NA`s.
`...` | for `upData`, one or more expressions of the form `variable=expression`, to derive new variables or change old ones.
`subset` | an expression that evaluates to a logical vector specifying which rows of `object` should be retained. The expressions should use the original variable names, i.e., before any variables are renamed but after `lowernames` takes effect.
`rename` | list or named vector specifying old and new names for variables. Variables are renamed before any other operations are done. For example, to rename variables `age` and `sex` to respectively `Age` and `gender`, specify `rename=list(age="Age", sex="gender")` or `rename=c(age=...)`.
`drop` | a vector of variable names to remove from the data frame
`keep` | a vector of variable names to keep, with all other variables dropped
`units` | a named vector or list defining `"units"` attributes of variables, in no specific order
`levels` | a named list defining `"levels"` attributes for factor variables, in no specific order. The values in this list may be character vectors redefining `levels` (in order) or another list (see `merge.levels` if using S-Plus).
`caplabels` | set to `TRUE` to capitalize the first letter of each word in each variable label
`moveUnits` | set to `TRUE` to look for units of measurements in variable labels and move them to a `"units"` attribute. If an expression in a label is enclosed in parentheses or brackets it is assumed to be units if `moveUnits=TRUE`.
`html` | set to `TRUE` to print conversion information as html vertabim at 0.6 size. The user will need to put `results='asis'` in a `knitr` chunk header to properly render this output.
`fracmiss` | the maximum permissable proportion of `NA`s for a variable to be kept. Default is to keep all variables no matter how many `NA`s are present.
`maxlevels` | the maximum number of levels of a character or categorical or factor variable before the variable is dropped
`minprev` | the minimum proportion of non-missing observations in a category for a binary variable to be retained, and the minimum relative frequency of a category before it will be combined with other small categories

### Value

a new data frame

### Author(s)

Frank Harrell, Vanderbilt University

### See Also

`sas.get`, `data.frame`, `describe`, `label`, `read.csv`, `strptime`, `POSIXct`,`Date`

### Examples

    ## Not run:
    dat <- read.table('myfile.asc')
    dat <- cleanup.import(dat)

    ## End(Not run)
    dat <- data.frame(a=1:3, d=c('01/02/2004',' 1/3/04',''))
    cleanup.import(dat, datevars='d', dateformat='%m/%d/%y', fixdates='year')

    dat <- data.frame(a=(1:3)/7, y=c('a','b1','b2'), z=1:3)
    dat2 <- upData(dat, x=x^2, x=x-5, m=x/10,
                   rename=c(a='x'), drop='z',
                   labels=c(x='X', y='test'),
                   levels=list(y=list(a='a',b=c('b1','b2'))))
    dat2
    describe(dat2)
    dat <- dat2    # copy to original name and delete dat2 if OK
    rm(dat2)
    dat3 <- upData(dat, X=X^2, subset = x < (3/7)^2 - 5, rename=c(x='X'))

    # Remove hard to analyze variables from a redundancy analysis of all
    # variables in the data frame
    d <- dataframeReduce(dat, fracmiss=.1, minprev=.05, maxlevels=5)
    # Could run redun(~., data=d) at this point or include dataframeReduce
    # arguments in the call to redun

    # If you import a SAS dataset created by PROC CONTENTS CNTLOUT=x.datadict,
    # the LABELs from this dataset can be added to the data.  Let's also
    # convert names to lower case for the main data file
    ## Not run:
    mydata2 <- cleanup.import(mydata2, lowernames=TRUE, sasdict=datadict)

    ## End(Not run)

[Package Hmisc version 4.0-3 Index]