Download the template R markdown file for this workshop.
In this exercise you will:
You need to have installed R, RStudio, and the necessary packages for
the course, including the ELMER
package. See how to
get set up for this course
data(Jaw, package="ELMER")
str(Jaw)
'data.frame': 10 obs. of 5 variables:
$ Age : Factor w/ 10 levels "<1","1+","2+",..: 1 2 3 4 5 6 7 8 9 10
$ Midage : num 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5
$ Number : int 71 250 210 59 44 34 12 9 8 7
$ JawLength: num 186 232 255 272 272 ...
$ SD : num 21.2 16.6 15.3 11.1 12.9 ...
Replicate the model fitting done by Brook & Arnold (1985) as shown in ELMER. Make sure you fit jaw length to the log of age, with and without using weights, and provide a graph to show the model.
Hint: Use weight=Number/SD^2
to get the weighted
model.
Use the value k=0.67 to fit the weighted and unweighted models taking the form:
\[y = A - B e^{-kt} \]
where t is the age of the deer.
Use these models to predict jaw length for the range of ages and plot
JawLength
against Age
with the fitted curves
added.
Vary the value of k to see if the model can be made to fit the data better.
You should compare your work with the solutions for this workshop.