Hi Jim,

Thank you for the suggestion. I think overlapped rectangles will well present the message. I'm now trying ggplot2.

Here is the code:

require(ggplot2)
rect_MNL_Delta <- data.frame(
        xmin <- c(1, 3, 5, 7, 9, 11, 13),
        xmax <- xmin + 1,
ymin <- c(16.7026, 14.9968, 16.0630, 17.7510, -5.01694, -.44146, 1.45884), ymax <- c(21.1602, 18.7613, 19.1367, 23.6730, 2.26564, 3.08630, 3.39865)
)
rect_GMNL <- data <- data.frame(
        xmin <- c(1, 3, 5, 7, 9, 11, 13),
        xmax <- xmin + 1,
        ymin <- c(17.20, 16.32, 15.86, 18.12, -8.86, -0.03, 0.95),
        ymax <- c(20.12, 18.60, 18.14, 22.29, 3.03, 3.57, 2.81)
)

ggplot() +
geom_rect(data = rect_MNL_Delta, aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax), fill = "blue", alpha = 0.1) + geom_rect(data = rect_GMNL, aes(xmin = xmin, xmax = xmax, ymin = ymin, ymax = ymax), fill = "green", alpha = 0.1)

The problem is that the second geom_rect() fully covered the first geom_rect(), instead of overlapping. Another issue is that I don't know how to set labels on x-axis, instead of the current ticks. I would like to have for instance 'Farmed cod' under the first rectangle.

Can you provide me some hints? Thank you.

Kind regards,

Xianwen

Jim Lemon wrote:
On 05/19/2013 09:19 AM, Xianwen Chen wrote:
Hi,

I want to plot grouped bars to compare 95% confidence interval estimates
from two models. Each bar represents a 95% confidence interval estimate
of a coefficient from one of the two models. Each group represents
confidence interval estimates of the same coefficient from the two models.

I think such a bar plot will nicely present whether 95% confidence
interval estimates of the same coefficient from the two models overlap.
All these confidence intervals do not start from the x axis.

I searched bar plot examples on Google. I found methods to plot bars in
groups by barplot(). I could only specify one offset for all confidence
interval estimates of the same model. I could not individually specify
an offset for each confidence interval estimate. Can someone please help
me on how I may proceed with individual offset for each of the bar in
the plot?

Hi Xianwen,
It seems that you want to line up either one or both of the estimates for each coefficient and then display the confidence intervals as bars around the estimates. If so, your ordinate (y-axis) won't be very interpretable unless you add one for each pair of coefficients. What I would initially suggest is that you display the coefficient values along a horizontal line and use "error bars" to show the confidence intervals. Here is an example:

coef<-c(3.6,3.2,5.7,6.0,1.2,1.3)
CIs<-c(1.2,1.4,2.7,2.6,3.1,2.9)
plot(0,xlim=c(0.5,3.5),ylim=range(c(-CIs,CIs)),type="n",
 xlab="Coefficients",ylab="95% confidence intervals",xaxt="n")
axis(1,at=c(0.8,1.2,1.8,2.2,2.8,3.2),
 labels=c("A1","A2","B1","B2","C1","C2"))
abline(h=0)
library(plotrix)
dispersion(c(0.8,1.2,1.8,2.2,2.8,3.2),rep(0,6),ulim=CIs,interval=TRUE)
boxed.labels(c(0.8,1.2,1.8,2.2,2.8,3.2),0,coef)

Jim

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