" Exercise 12.2 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 Data from R. Harrington & C. Shortall, Rothamsted Research Version 1, 14/08/2015 " " Set working directory - change to location of your data file " \SET [WORKINGDIRECTORY='d:/stats4biol/data/'] " Read data from working directory " FILEREAD [NAME='HEREFORD.DAT'; IMETHOD=read] FGROUPS=no " Transform the data to logs with offset of 0.5 " CALCULATE logWt=LOG10(WetWeight+0.5) " Plot data " DGRAPH Y=logWt; X=Year " Fit SLR " MODEL Y=logWt FIT [FPROBABILITY=yes; TPROBABILITY=yes] Year " Save fitted values and standardized residuals " RKEEP FITTEDVALUES=fval; RESIDUALS=res " Residual plots based on standardized residuals " DRESIDUALS [RESIDUALS=res; FITTEDVALUES=fval] METHOD=fittedvalues,normal,histogram,absresidual " Plot fitted model " RGRAPH [CIPLOT=yes] " Predict for 2010 and save prediction with SE " PREDICT [PREDICTIONS=pred; SE=SEpred] CLASSIFY=Year; LEVELS=2010 " Save residual df " RKEEP DF=resdf " Obtain critical value from t-distribution " CALCULATE tcrit=EDT(0.975;resdf) " Calculate 95% CI for prediction " CALCULATE lower=pred-tcrit*SEpred CALCULATE upper=pred+tcrit*SEpred PRINT STRUCTURE=lower,pred,upper " Print prediction and 95% CI on back-transformed scale " PRINT STRUCTURE=10**(lower,pred,upper)-0.5 " Check residuals for temporal correlation - data is in year order " " Plot residual against that from previous year " DGRAPH res; shift(res;-1) " Correlation between residual and that from previous year " FCORR [PRINT=corr,test] shift(res;0,1) " Plot residuals in year order " PEN 1; METHOD=line DGRAPH res; Year " End of File "