# [R] Multiple density curves

Gabor Grothendieck ggrothendieck at gmail.com
Fri Aug 11 14:01:25 CEST 2006

```The code below was missing the breaks= argument to hist.
I had not noticed because coincidentally both give the same
breaks anways thus the following corrected version gives the
same plot in this case but might not in other cases.

# data
DF <- structure(list(SEQ = structure(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13), .Label = c("A", "B", "C", "D", "E", "F", "G", "H",
"I", "J", "K", "L", "M"), class = "factor"), A1 = c(532.5, 25.5,
265.2, 245.55, 546.52, 243.25, 452.55, 15.14, 543.4, 54.4, 646.5,
645.4, 646.54), A2 = c(554.5, 35.5, 522.2, 521.56, 141.52, 32.56,
635.56, 16.54, 646.56, 654.5, 64.54, 614.46, 634.46)), .Names = c("SEQ",
"A1", "A2"), class = "data.frame", row.names = c("1", "2", "3",
"4", "5", "6", "7", "8", "9", "10", "11", "12", "13"))

# determine breaks and y limits of the combined plot
breaks <- hist(c(DF\$A1, DF\$A2), plot = FALSE)\$breaks
ymax1 <- max(hist(DF\$A1, breaks = breaks, plot = FALSE)\$intensities)
ymax2 <- max(hist(DF\$A2, breaks = breaks, plot = FALSE)\$intensities)
ylim <- c(0, max(ymax1, ymax2))

# draw the two histograms and two densities
hist(DF\$A1, ang = 45, col = "red", ylim = ylim,
breaks = breaks, freq = FALSE, density = 10)
lines(density(DF\$A1), col = "red")
hist(DF\$A2, ang = -45, col = "blue", add = TRUE,
breaks = breaks, freq = FALSE, density = 10)
lines(density(DF\$A2), col = "blue")

On 8/11/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> From your description I assume you want both histograms
> and the densities all on the same chart.  With existing R
> graphics I am not sure that there really is a simple way to
> do that.
>
> That aside, note that the hist function returns a list of
> components that includes
>
> - breaks, defining the breakpoints of the histogram
> - intensities defining the heights of the histogram bars
>
> We can use these two to determine the breaks and y limits
> of the combined plot and then use the breaks= and ylim=
> arguments of hist to specify them so that both histograms
> can be drawn on the same chart.  We also use freq=FALSE
> in the hist calls to draw intensities rather than counts.  On
> the second hist call we use add=TRUE to cause it to be drawn
> on the existing plot.
>
> The other problem is to distinguish the superimposition of
> the bars and that can be handled by using shading lines of
> different colors and angles using the col= and angle= and
> density= arguments of hist.
>
>
> # data
> DF <- structure(list(SEQ = structure(c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
> 11, 12, 13), .Label = c("A", "B", "C", "D", "E", "F", "G", "H",
> "I", "J", "K", "L", "M"), class = "factor"), A1 = c(532.5, 25.5,
> 265.2, 245.55, 546.52, 243.25, 452.55, 15.14, 543.4, 54.4, 646.5,
> 645.4, 646.54), A2 = c(554.5, 35.5, 522.2, 521.56, 141.52, 32.56,
> 635.56, 16.54, 646.56, 654.5, 64.54, 614.46, 634.46)), .Names = c("SEQ",
> "A1", "A2"), class = "data.frame", row.names = c("1", "2", "3",
> "4", "5", "6", "7", "8", "9", "10", "11", "12", "13"))
>
> # determine breaks and y limits of the combined plot
> breaks <- hist(c(DF\$A1, DF\$A2), plot = FALSE)\$breaks
> ymax1 <- max(hist(DF\$A1, breaks = breaks, plot = FALSE)\$intensities)
> ymax2 <- max(hist(DF\$A2, breaks = breaks, plot = FALSE)\$intensities)
> ylim <- c(0, max(ymax1, ymax2))
>
> # draw the two histograms and two densities
> hist(DF\$A1, ang = 45, col = "red", ylim = ylim, freq = FALSE, density = 10)
> lines(density(DF\$A1), col = "red")
> hist(DF\$A2, ang = -45, col = "blue", add = TRUE, freq = FALSE, density = 10)
> lines(density(DF\$A2), col = "blue")
>
> On 8/10/06, Davendra Sohal <dsohal at gmail.com> wrote:
> > Hi,
> >
> > I am new to R...a recent convert from SAS.
> > I have a dataset that looks like this:
> >
> > SEQ    A1    A2
> > A    532.5    554.5
> > B    25.5    35.5
> > C    265.2    522.2
> > D    245.55    521.56
> > E    546.52    141.52
> > F    243.25    32.56
> > G    452.55    635.56
> > H    15.14    16.54
> > I    543.4    646.56
> > J    54.4    654.5
> > K    646.5    64.54
> > L    645.4    614.46
> > M    646.54    634.46
> >
> > I want to make a histogram each for A1 and A2, with density curves, on the
> > same plot so that I can see how they overlap.
> >
> > Please let me know some simple code for this.
> >
> > I looked at ldahist but it was complicated. Anything simpler?
> >
> > Thanks a lot,
> > -DS.
> >
> >        [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>

```