I am attempting a 2-way ANOVA with repeated measures using the aov() function in R. I am trying to compare average heights ("X1" and "X2") of algae by treatment ("CODE") and site over time ("MONTH"). The data I entered into R is already averaged. Therefore each row = one observation per treatment, per code, per month (1-60). I have created a column called "ID" to identify each observation (1-60).
head(HNME1) ID MONTH SITE CODE X1 X2 1 OCT BPT C+ 3.526667 3.440000 2 OCT BPT C- 3.296667 3.540000 3 OCT BPT U+ 2.146667 1.000000 4 OCT BPT U- 3.146667 3.016667 5 OCT BPT P 2.827778 2.122222 6 OCT FLC C+ 3.620000 1.990000
However, when running this code:
"x1.aov<-aov(X1 ~ MONTH * SITE * CODE + Error(ID/(SITE * CODE)), data=HNME1)"
I am not receiving any p-values in my ANOVA summary. I have read other forums telling me to make the ID values into factors.
"HNME1$ID <- factor(HNME1$ID)"
I have tried this and received the error:
"Error () model is singular." However, I do not have any gaps or missing data values. I am not sure what else could be going wrong.
Just messing around - I tried a one-way ANOVA with "MONTH" where "ID" was and this produced p-values...
Any suggestions/ help would be much appreciated! Thank you.