Ggplot2 using same value for all X values on graph

As you asked for the rational for using geom_point instead of geom_dotplot: What geom_dotplot does is creating bins - in your case along the y-axis (your variable Copies.Left4.ng ) and count the number of occurrences in those bins. Each occurrence is represented by one point. geom_dotplot puts these numbers/bins then somewhere on the x-axis which you have chosen.

A good case for using geom_dotplot in my opinion is when you have to count occurences for categorical data like in this example:

library(ggplot2)

ggplot(ToothGrowth, aes(x=factor(dose), y=len)) + 
  geom_dotplot(binaxis='y', stackdir='center')

As you can see, I have made the dose-data a factor in the aesthetics. This will make the ticks on the x-axis equidistant. This is OK for this dataset.

But your dataset is non-categorical for Hour and for Copies (I have chosen this a variable name.) I have taken a little simplified data frame than yours and defined it in read.table. This is then followed by making the plot with geom_point.

df <- read.table(text = "
  Hour  Copies
  46.0  8807
  72    6781
  72    4311
  29.5  3313
  42    3096
  29.5  2807
  42    2141
  24    37
  0     31
  24    24
  -24   17
", header = TRUE)

library(ggplot2)

ggplot(df, aes(x=Hour, y=Copies)) + geom_point()

You may find further useful information in R-Graphics Cookbook.