[R] column width in .dbf files using write.dbf ... to be continued

[Bastien.Ferland-Raymond at mrn.gouv.qc.ca]

Hello Arnaud,

You posted this question a long long time ago, however I found your answer so I decided to post it anyway in case somebody else have the same problem as you and me.

You were actually very close in finding your solution.  The function DoWritedbf is an internal function from the foreign package.  To access it outside of the package just do:

foreign:::DoWritedbf

so in your line:

invisible(.Call(foreign:::DoWritedbf, as.character(file), dataframe,
  as.integer(precision), as.integer(scale), as.character(DataTypes)))

It is explain here: http://stackoverflow.com/questions/2165342/r-calling-a-function-from-a-namespace

Sorry for the delay in my answer...

Bastien Ferland-Raymond, M.Sc. Stat., M.Sc. Biol.
Division des orientations et projets spéciaux
Direction des inventaires forestiers
Ministère des Ressources naturelles

In reply to :
#####
Dear UseRs,
I did not have any answer to my previous message ("Is there a way to define "manually" columns width when using write.dbf function from the library foreign ?"), so I tried to modify write.dbf function to do what I want.
Here is my modified version :
write.dbfMODIF <- function (dataframe, file, factor2char = TRUE, max_nchar = 254, width = d)
{
    allowed_classes <- c("logical", "integer", "numeric", "character",
        "factor", "Date")
    if (!is.data.frame(dataframe))
        dataframe <- as.data.frame(dataframe)     if (any(sapply(dataframe, function(x) !is.null(dim(x)))))
        stop("cannot handle matrix/array columns")     cl <- sapply(dataframe, function(x) class(x[1L]))     asis <- cl == "AsIs"
    cl[asis & sapply(dataframe, mode) == "character"] <- "character"     if (length(cl0 <- setdiff(cl, allowed_classes)))
        stop("data frame contains columns of unsupported class(es) ",
            paste(cl0, collapse = ","))

    m <- ncol(dataframe)
    DataTypes <- c(logical = "L", integer = "N", numeric = "F",
        character = "C", factor = if (factor2char) "C" else "N",
        Date = "D")[cl]
    for (i in seq_len(m)) {
        x <- dataframe[[i]]
        if (is.factor(x))
            dataframe[[i]] <- if (factor2char)
                as.character(x)
            else as.integer(x)
        else if (inherits(x, "Date"))
            dataframe[[i]] <- format(x, "%Y%m%d")
    }
    precision <- integer(m)
    scale <- integer(m)
    dfnames <- names(dataframe)
    for (i in seq_len(m)) {
        nlen <- nchar(dfnames[i], "b")
        x <- dataframe[, i]
        if (is.logical(x)) {
            precision[i] <- 1L
            scale[i] <- 0L


        }

        else if (is.integer(x)) {
            rx <- range(x, na.rm = TRUE)
            rx[!is.finite(rx)] <- 0
            if (any(rx == 0))
                rx <- rx + 1
            mrx <- as.integer(max(ceiling(log10(abs(rx)))) +
                3L)
            precision[i] <- min(max(nlen, mrx), 19L)
            scale[i] <- 0L


        }

        else if (is.double(x)) {
            precision[i] <- 19L
            rx <- range(x, na.rm = TRUE)
            rx[!is.finite(rx)] <- 0
            mrx <- max(ceiling(log10(abs(rx))))
            scale[i] <- min(precision[i] - ifelse(mrx > 0L, mrx +
                3L, 3L), 15L)


        }

        else if (is.character(x)) {
        if (width == "d") {
                   mf <- max(nchar(x[!is.na(x)], "b"))
                p <- max(nlen, mf)
                if (p > max_nchar)
                    warning(gettext("character column %d will be truncated
to %d bytes",
                      i, max_nchar), domain = NA)
                precision[i] <- min(p, max_nchar)
                scale[i] <- 0L


        } else {


            if (width > max_nchar)
                    warning(gettext("character column %d will be truncated
to %d bytes",
                      i, max_nchar), domain = NA)
                precision[i] <- min(width, max_nchar)


        }

        }

        else stop("unknown column type in data frame")
    }
    if (any(is.na(precision)))
        stop("NA in precision")
    if (any(is.na(scale)))
        stop("NA in scale")
    invisible(.Call(DoWritedbf, as.character(file), dataframe,
        as.integer(precision), as.integer(scale), as.character(DataTypes))) }
However, when I wanted to use this function ... it does not find the DoWritedbf function that is called in the last lines (a function written in C).
Is there a way to temporally replace the original write.dbf function by this one in the foreign package ?
Thanks,
Arnaud
R version 2.10.0 (2009-10-26)
i386-pc-mingw32
######