masthead
 

Data Input and Determination of Value for Transformation

DATA ABUN; /* input data */
INPUT MONTH /* month sampled */
DAY /* day sampled */
YEAR /* year sampled */
PERIOD /* six-month period dating from the start of monitoring */
S1 /* dummy variable - has value of 1 while treatment
basin pH is 5.6, value of 0 otherwise */
S2 /* dummy variable - has value of 1 while treatment
basin is pH 5.1, value of 0 otherwise */
REF /* abundance of K. taurocephala in reference basin */
TRT; /* abundance of K. taurocephala in treatment basin */
RATIO = (TRT+1)/(REF+1); /* compute ratio of treatment to reference abundance */
LOGRATIO = LOG10(RATIO); /* compute log transformation of ratio */
LOGREF = LOG10(REF); /* compute log transformation of original data */

PROC SUMMARY NWAY; /* calculate mean and SD of ratios for each year */
CLASS YEAR; VAR RATIO;
OUTPUT OUT=SUMRY /* output SDs */
MEAN=MRATIO STD=SD;
DATA SUMRY; SET SUMRY; /* calculate log of mean and SD */
LOGRATIO = LOG10(MRATIO);
LOGSD = LOG10(SD);
PROC PLOT; /* plot log SD vs log mean */
PLOT LOGSD*LOGRATIO;

PROC REG; /* regress log SD on log mean */
MODEL LOGSD = LOGRATIO;



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