[Rd] overriding "summary.default" or "summary.data.frame". How?

[Uwe Ligges]

Simple answer: Never ever override R base functionality.

Best,
Uwe Ligges





On 20.03.2012 16:24, Paul Johnson wrote:
> I suppose everybody who makes a package for the first time thinks "I
> can change anything!" and then runs into this same question. Has
> anybody written out information on how a package can override
> functions in R base in the R 2.14 (mandatory NAMESPACE era)?
>
> Suppose I want to alphabetize variables in a summary.data.frame, or
> return the standard deviation with the mean in summary output.  I'm
> pasting in a working example below.  It has new "summary.factor"
> method. It also has a function summarize that I might like to use in
> place of summary.data.frame.
>
> How would my new methods "drop on top" of R base functions?  It
> appears my functions (summarizeFactors) can find my summary.factor,
> but R's own summary uses its own summary.factor.
>
>
> ## summarizeNumerics takes a data frame or matrix, scans the columns
> ## to select only the numeric variables.  By default it alphabetizes
> ## the columns (use alphaSort = FALSE to stop that). It then
> ## calculates the quantiles for each variable, as well as the mean,
> ## standard deviation, and variance, and then packs those results into
> ## a matrix. The main benefits from this compared to R's default
> ## summary are 1) more summary information is returned for each
> ## variable, and the results are returned in a matrix that is easy to
> ## use in further analysis.
> summarizeNumerics<- function(dat, alphaSort = TRUE,  digits = max(3,
> getOption("digits") - 3)){
>    if (!is.data.frame(dat)) dat<- as.data.frame(dat)
>    nums<- sapply(dat, is.numeric)
>    datn<- dat[ , nums, drop = FALSE]
>    if (alphaSort) datn<- datn[ , sort(colnames(datn)), drop = FALSE]
>    sumdat<- apply(datn, 2, stats::quantile, na.rm=TRUE)
>    sumdat<- rbind(sumdat, mean= apply(datn, 2, mean, na.rm=TRUE))
>    sumdat<- rbind(sumdat, sd= apply(datn, 2, sd, na.rm=TRUE))
>    sumdat<- rbind(sumdat, var= apply(datn, 2, var, na.rm=TRUE))
>    sumdat<- rbind(sumdat, "NA's"=apply(datn, 2, function(x) sum(is.na(x))))
>    signif(sumdat, digits)
> }
>
>
> summary.factor<- function(y, numLevels) {
>    ## 5 nested functions to be used later
>
>    divr<- function(p=0){
>      ifelse ( p>0&  p<  1, -p * log2(p), 0)
>    }
>    entropy<- function(p){
>      sum ( divr(p) )
>    }
>    maximumEntropy<- function(N) -log2(1/N)
>    normedEntropy<- function(x) entropy(x)/ maximumEntropy(length(x))
>    nas<- is.na(y)
>    y<- factor(y)
>    ll<- levels(y)
>    tbl<- table(y)
>    tt<- c(tbl)
>    names(tt)<- dimnames(tbl)[[1L]]
>    o<- sort.list(tt, decreasing = TRUE)
>    if (length(ll)>  numLevels){
>      toExclude<- numLevels:length(ll)
>      tt<- c(tt[o[-toExclude]], `(All Others)` = sum(tt[o[toExclude]]),
> `NA's`=sum(nas))
>    }else{
>      tt<- c(tt[o], `NA's`=sum(nas))
>    }
>    props<- prop.table(tbl);
>    tt<- c(tt, "Entropy"=entropy(props), "NormedEntropy"= normedEntropy(props))
> }
>
>
> ## Takes a data frame or matrix, scans the columns to find the
> ## variables that are not numeric and keeps them. By default it
> ## alphabetizes them (alphaSort = FALSE to stop that).  It then treats
> ## all non-numeric variables as if they were factors, and summarizes
> ## each in a say that I find useful. In particular, for each factor,
> ## it provides a table of the most frequently occurring values (the
> ## top "numLevels" values are represented).  As a diversity indictor,
> ## it calculates the Entropy and NormedEntropy values for each
> ## variable.  Note not all of this is original. It combines my code
> ## and R code from base/summary.R
> summarizeFactors<- function(dat = NULL, numLevels = 10, alphaSort =
> TRUE, digits = max(3, getOption("digits") - 3))
> {
>
>    ##copies from R base::summary.R summary.data.frame
>    ncw<- function(x) {
>      z<- nchar(x, type="w")
>      if (any(na<- is.na(z))) {
>              # FIXME: can we do better
>        z[na]<- nchar(encodeString(z[na]), "b")
>      }
>      z
>    }
>
>    if (!is.data.frame(dat)) dat<- as.data.frame(dat)
>    ##treat any nonnumeric as a factor
>    factors<- sapply(dat, function(x) {!is.numeric(x) })
>    ##If only one factor, need drop=FALSE.
>    datf<- dat[ , factors, drop = FALSE]
>    if (alphaSort) datf<- datf[ , sort(colnames(datf)), drop = FALSE]
>    z<- lapply(datf, summary.factor, numLevels=numLevels)
>    nv<- length(datf)
>    nm<- names(datf)
>    lw<- numeric(nv)
>    nr<- max(unlist(lapply(z, NROW)))
>    for(i in 1L:nv) {
>      sms<- z[[i]]
>      lbs<- format(names(sms))
>      sms<- paste(lbs, ":", format(sms, digits = digits), "  ",
>                   sep = "")
>      lw[i]<- ncw(lbs[1L])
>      length(sms)<- nr
>      z[[i]]<- sms
>    }
>    z<- unlist(z, use.names=TRUE)
>    dim(z)<- c(nr, nv)
>    if(any(is.na(lw)))
>      warning("probably wrong encoding in names(.) of column ",
>              paste(which(is.na(lw)), collapse = ", "))
>      blanks<- paste(character(max(lw, na.rm=TRUE) + 2L), collapse = " ")
>    pad<- floor(lw - ncw(nm)/2)
>    nm<- paste(substring(blanks, 1, pad), nm, sep = "")
>    dimnames(z)<- list(rep.int("", nr), nm)
>    attr(z, "class")<- c("table")
>    z
> }
>
> ##
> ## want to override summary.data.frame, but confusing.  When
> ## will R find my summary.data.frame, when will it find the one in base.
> ## use ... for numLevels, digits, alphaSort
> summarize<- function(dat, ...)
> {
>    dots<- list(...)
>    dotnames<- names(dots)
>    ## next should give c("digits", "alphaSort")
>    nnames<-  names(formals(summarizeNumerics))[-1L]
>    ## names that need keeping if in dots:
>    keepnames<- dotnames %in% nnames
>    if( sum(keepnames)>  0 ) {
>      argList<- modifyList( list("dat"=quote(dat)), dots[keepnames] )
>      datn<- do.call("summarizeNumerics", argList)
>     } else {
>      datn<- do.call("summarizeNumerics", args=list("dat"= quote(dat)))
>    }
>
>    ## all ... can go to summarizeFactors
>    datf<- summarizeFactors(dat, ...)
>
>    value<- list(numerics = datn, factors = datf)
>    value
> }
>
>
>
>
> set.seed(23452345)
> x1<- gl(12,2, labels=LETTERS[1:12])
> x2<- gl(8,3, labels=LETTERS[12:24])
> z1<- rnorm(24)
> a1<- rnorm(24, mean=1.2, sd = 1.7)
> a2<- rpois(24, lambda=10 + a1)
> a3<- rgamma(24, 0.5, 4)
> b1<- rnorm(24, mean=1.3, sd = 1.4)
> dat<- data.frame(z1, a1, x2, a2, x1, a3, b1)
> summary(dat)
>
>
> summarize(dat)
>
>
> summarizeNumerics(dat)
> summarizeFactors(dat, numLevels=5)
>
> summarize(dat, alphaSort=FALSE)
>
> summarize(dat, digits=6, alphaSort=FALSE)
>
> summarize(dat, digits=22, alphaSort=FALSE)
>
> summarize(dat, numLevels= 2)
>
> datsumm<- summarize(dat)
>
> datsumm$numerics
> datsumm[[1]] ## same: gets numerics
>
> datsumm$factors
> datsumm[[2]]
>
>
> ## Use numerics output to make plots. First,
> ## transpose gives varnames x summary stat matrix
> datsummNT<- t(datsumm$numerics)
> datsummNT<- as.data.frame(datsummNT)
>
> plot(datsummNT$mean, datsummNT$var, xlab="The Means", ylab="The Variances")
>
> plot(datsummNT$mean, datsummNT$var, xlab="The Means", ylab="The
> Variances", type="n")
> text(datsummNT$mean, datsummNT$var, labels=rownames(datsummNT))
>
> ## Here's a little plot wrinkle.  Note variable names are "out to the
> ## edge" of the plot. If names are longer they don't stay inside
> ## figure. See?
>
> ## Make the variable names longer
>
> rownames(datsummNT)
> rownames(datsummNT)<- c("boring var","var with long name", "tedious
> name var", "stupid varname", "buffoon not baboon")
> plot(datsummNT$mean, datsummNT$var, xlab="The Means", ylab="The
> Variances", type="n")
> text(datsummNT$mean, datsummNT$var, labels=rownames(datsummNT), cex=0.8)
> ## That's no good. Names across the edges
>
> ## We could brute force the names outside the edges like this
> par(xpd=T)
> text(datsummNT$mean, datsummNT$var, labels=rownames(datsummNT), cex=0.8)
> ## but that is not much better
> par(xpd=F)
>
> ## Here is one fix. Make the unused space inside the plot larger by
> ## making xlim and ylim bigger.  I use the magRange function from
> ## rockchalk to easily expand range to 1.2 times its current size.
> ## otherwise, long variable names do not fit inside plot. magRange
> ## could be asymmetric if we want, but this use is symmetric.
> library(rockchalk)
>
> rownames(datsummNT)
> rownames(datsummNT)<- c("boring var","var with long name", "tedious
> name var", "stupid varname", "buffoon not baboon")
> plot(datsummNT$mean, datsummNT$var, xlab="The Means", ylab="The
> Variances", type="n", xlim=magRange(datsummNT$mean, 1.2),
> ylim=magRange(datsummNT$var, 1.2))
> text(datsummNT$mean, datsummNT$var, labels=rownames(datsummNT), cex=0.8)
>
> ## Here's another little plot wrinkle.
> ## If we don't do that to keep the names in bounds, we need some
> ## fancy footwork.  Note when a point is near the edge, I make sure
> ## the text prints toward the center of the graph.
> plot(datsummNT$mean, datsummNT$var, xlab="The Means", ylab="The Variances")
> ## calculate label positions. This is not as fancy as it could be.
> ## If there were lots of variables, we'd have to get smarter about
> ## positioning labels on above, below, left, or right.
> labelPos<- ifelse(datsummNT$mean - mean(datsummNT$mean, na.rm=T)>  0, 2, 4)
> text(datsummNT$mean, datsummNT$var, labels=rownames(datsummNT),
> cex=0.8, pos=labelPos)
>
>
>
> x<- data.frame(x=rnorm(100), y = gl(50,2), z = rep(1:4, 25), ab = gl(2,50))
>
> summarize(x)
> summarize(x, numLevels=15)
>
> sumry<- summarize(x)
> sumry[[1]] ##another way to get the numerics output
> sumry[[2]] ##another way to get the factors output
>
> dat<- data.frame(x=rnorm(100), y = gl(50,2), z = factor(rep(1:4, 25),
> labels=c("A","B","C","D")), animal=factor(ifelse(runif(100)<  0.2,
> "cow", ifelse(runif(100)<  0.5,"pig","duck"))))
>
> summarize(dat)
>
> dat<- read.table(url("http://pj.freefaculty.org/guides/stat/DataSets/USNewsCollege/USNewsCollege.csv"),
> sep=",")
>
> colnames(dat)<- c("fice", "name", "state", "private", "avemath", "aveverb",
>      "avecomb", "aveact", "fstmath", "trdmath", "fstverb", "trdverb",
>      "fstact", "trdact", "numapps", "numacc", "numenr", "pctten",
>      "pctquart", "numfull", "numpart", "instate", "outstate",
>      "rmbrdcst", "roomcst", "brdcst", "addfees", "bookcst", "prsnl",
>      "pctphd", "pctterm", "stdtofac", "pctdonat", "instcst", "gradrate")
>
> dat$private<- factor(dat$private, labels=c("public","private"))
> sumry<- summarize(dat, digits=2)
> sumry
>
> sumry[[1]]
> sumry[[2]]
>
> summarize(dat[ , c("fice","name","private","fstverb","avemath")], digits=4)
>
>