R: in Barplot Midpoints Are Not Centered W.R.T. Bars

R: in barplot midpoints are not centered w.r.t. bars

If you save the barplot() result as an object you get the midpoints for the bars.

bp <- barplot(y)
bp
     [,1]
[1,]  0.7
[2,]  1.9
[3,]  3.1
[4,]  4.3
[5,]  5.5

If you use them now in other plotting functions those midpoints should be as x values. In call plot(bp) they are used as y values and x values are sequence numbers 1,2,3,4,5 - so they do not correspond to midpoints.

Providing also y values, points are plotted as expected.

bp <- barplot(y)
points(bp,c(10,20,30,40,50))

Points of dotplot are not centered on the corresponding barplot bars

As mentioned by @s_t, you have to write:

library(ggplot2)
ggplot(d, aes(x=a, y=d, fill=as.factor(c))) + 
  geom_bar(stat="identity", position="dodge")+
  geom_point(aes(y = b / 10000), 
             position = position_dodge(.9))

Data

d = data.frame(a = sort(rep(LETTERS[1:5],2)),
               b = c(55,123,222,234,233,187,564,325,112,105),
               c = rep(c(2,1),5),
               d = c(0.07,0.05,0.04,0.03,0.03,0.04,0.06,0.01,0.02,0.01))

How to center bars in R barplot() around ticks

Part1 <- c(2,4,9,18,20)
Part2 <- c(2,5,1,4,0)
counts <- rbind(Part1, Part2)
colnames(counts) <- c(1,2,3,4,5)

x<-barplot(counts, 
  axes = FALSE,  
  space = 0,         
  col = c("darkgreen", "red"),
  xlim = c(0, 5*1.50),
  ylim = c(0,60)
)

#create positions for tick marks, one more than number of bars
ticks <- seq_len(length(counts) + 1)
axis(side = 2, pos = 0)
#adding x-axis with offset positions, with ticks, but without labels
axis(side = 1, at = ticks - 0.5, labels = FALSE)

Labels do not fit to my bin center in histogram

The x axis values are not necessarily interger values. The barplot function returns the x values used during plotting. Try

bp<-barplot(data.norm, beside=TRUE, col=c("grey10","grey20","grey30","grey40","grey50","grey60"))
text(bp, par("usr")[3], labels=my.names, srt=45, pos=2, xpd=TRUE,offset=0.01)

instead.

Labelling axis in a plot

You mean something like this?
Which is based on this post.
There are probably more sophisticated ways to do this.

# Barplot
bp<-barplot(as.matrix(condition), 
        col=c("darkblue","red"),
        xlab="month",
        ylab="subject count",
        main="Monthly condition",
        ylim=c(0, 140)) 

# x-axis labels
axis(1, at = bp,
     labels=c("month 1", "month 2", "month 3", "month 4", "month 5"),
     cex.axis=1.2)

# Add legend
legend(5.25,140.1,
       c("good","poor"), 
       fill=c("darkblue","red"),
       title="condition")

Which will give:

You probably want to do something on the position of your legend, and I don't think that specifying the xlab is necessary if you're going to label each bar individually.
I won't comment on the choice of colours :)

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