" Exercise 8.8

 Statistical Methods in Biology: Design and Analysis of Experiments and Regression
 by S.J. Welham, S.A. Gezan, S.J. Clark & A. Mead (2014)
 Chapman & Hall/CRC Press, Boca Raton, Florida. ISBN: 978-1-4398-0878-8
 Version 1, 25/08/2014 "

" Set working directory - change to location of your data file "
\SET [WORKINGDIRECTORY='d:/stats4biol/data/']

" Read data from working directory "
FILEREAD [NAME='CALCIUM.DAT'; IMETHOD=read] FGROUPS=no,yes,no

" Modify levels of Calcium factor to include numerical levels "
FACTOR [MODIFY=yes; LEVELS=!(1,5,10,20)] IDENTIFIER=Calcium

" Plot data "
DGRAPH Y=Length; X=Calcium

" Fit quadratic polynomial "
TREATMENTSTRUCTURE POL(Calcium;2)
ANOVA [FPROBABILITY=yes; PSE=differences,means] Y=Length

" Display equation of fitted quadratic polynomial & save coefficients "
APOLYNOMIAL Calcium; COEFF=coeff
PRINT coeff[1][]

" Save treatment means "
AKEEP TERMS=Calcium; MEANS=Means
VTABLE TABLE=Means; VARIATE=vMeans; CLASS=!P(fC)

" Plot data with fitted means and polynomial trend "
VARIATE iCalcium; VAL=!(1...20)
CALCULATE iFit = coeff[1][0] + coeff[1][1]*iCalcium + coeff[1][2]*iCalcium**2
PEN 3; METHOD=line; SYMBOLS=0
DGRAPH Length,vMeans,iFit; X=Calcium,fC,iCalcium; PEN=1,2,3; \
  DESCRIPTION='Raw data','Treatment means','Fitted polynomial'

" End of File "