# Decimal log scale on a plot

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R only does natural (neperian) log scales by default, and this is lame.

Here is a simple code to do decimal log scale, pretty much a requirement for scientists…

The force(x/y)lim options works for natural and log scales (for the later case, you need to specify the power of 10 that you want : c(-2,2) fixes the limit from 0.01 to 100)

drawlogaxis <- function(side,range) { par(tck=0.02) # d <- log(range,10) d <- range mlog <- floor(min(d)) Mlog <- ceiling(max(d)) SeqLog <- c(mlog:Mlog) Nlog <- (Mlog-mlog)+1 axis(side,at=SeqLog,labels=10^SeqLog) ats <- log(seq(from=2,to=9,by=1),10) mod <- NULL for(i in SeqLog) { mod <- c(mod,rep(i,length(ats))) } ats <- rep(ats,Nlog) ats <- ats+mod par(tck=0.02/3) axis(side,at=ats,labels=NA) } logplot <- function(x,y,log='xy',...,forceylim=c(0,0),forcexlim=c(0,0)) { par(tck=0.02) xlg <- FALSE ylg <- FALSE if('x'%in%strsplit(log,'')[[1]]){x <- log(x,10);xlg=TRUE} if('y'%in%strsplit(log,'')[[1]]){y <- log(y,10);ylg=TRUE} yl <- ifelse(forceylim==c(0,0),range(y),forceylim) xl <- ifelse(forcexlim==c(0,0),range(x),forcexlim) plot(x,y,...,axes=FALSE,ylim=yl,xlim=xl) if(xlg){drawlogaxis(1,xl)}else{axis(1,at=pretty(xl),labels=pretty(xl))} if(ylg){drawlogaxis(2,yl)}else{axis(2,at=pretty(yl),labels=pretty(yl))} box() } addlog <- function(x,y,log='xy',...) { xlg <- FALSE ylg <- FALSE if('x'%in%strsplit(log,'')[[1]]){x <- log(x,10);xlg=TRUE} if('y'%in%strsplit(log,'')[[1]]){y <- log(y,10);ylg=TRUE} points(x,y,...) }

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